Evidence for ET is mounting daily, but not proven.

[Colin Robinson]

There are many possible reasons why we are not obviously embedded in a galactic civilisation. One of the most likely is that the nearest expansive civilisation is still too far away to have got here yet.

Here#s a good summary by Milan Cirkovic of the possibilities; none of them are entirely compelling.
http://arxiv.org/abs/0907.3432

Just had a look at Milan Cirkovic's article, which I found very informative and thought-provoking. I liked the comparison he makes between Fermi's Paradox and Olbers' Paradox.

Also liked his calm consideration of the possibility that now and then a galaxy like ours experiences catastrophes which, as he puts it, reset and resynchronize the clocks of evolution throughout that galaxy's habitable zone.

It is a plausible explanation for the fact that we don't see evidence of highly advanced technology all over the galaxy: evolution has not yet had time to get that far since the last big catastrophe, which could have occurred just a few billion years back.

[Trakar]

That's certainly an interesting perspective! A generation ship that was permanently self-sufficient in deep space seems like a far greater technological hurdle to overcome than one designed to survive a transit to another system.

In your scenario, why should a generation ship even leave its home system? Why not simply subsist in the same orbit as the home planet?

There are already hundreds of thousands (or more) such colonies throughout the home system, the designers of this one chose to set a different course.

[Colin Robinson]

Or perhaps not. Do we see it as our moral duty to go and help every ant hill?

We are certainly curious about ants, and we certainly see similarities between ant societies and our own. That doesn't mean we go and interact with every ant hill on Earth on an every day basis.

It's an interesting concept that if an ET life-form was more intelligent than humans, it might regard us as we regard social insects.

The only social insect that regularly receives help from humans is the bee. That is because it is useful enough to be treated as a domestic animal. Human beings might not like to be treated that way by ETIs, but perhaps we would have no choice in the matter.

Or perhaps ETIs would see us as as wasps: not a creature to be domesticated, but a potential source of trouble. We know the wasps can't destroy our civilization, but we also know they can inflict a nasty painful sting.

Maybe that is why we haven't heard from any intelligent ETs. Just as a sensible human wouldn't want to attract attention from a wasps' nest, the ETIs don't want to attract the attention of a planet full of humans.

The biggest danger is that they might come to see us as termites...

Which implies that if we humans do visit to a planet with ETI, then we will need to strictly avoid making a meal of local building materials; even if the locals make their houses out of ginger-bread.


Note that I'm talking about ET. ET means extra-terrestrial life. If you want to use the term "ET", I will hold you to using it in the correct manner. ET does not mean extra-terrestrial technological civilizations.


On a more serious note, I agree this is an important distinction. Here on Earth, life has been present for billions of years. However, a technological civilization, capable of transmitting and receiving radio signals, only started to emerge in the late 19th century. Now that it's here, it may continue to exist for a long time; or it may not.

[Garrison]

Another thought on why there maybe an interstellar civilization or several around us but they aren't here. Perhaps their method of interstellar travel is at some level analogous to sailing the oceans before the age of steam in that there are functional equivalents of wind and currents that the vessels follow, creating natural routes for exploration and expansion. Now if Earth isn't along such a route then the aliens might well be unable or unwilling to come here. Alternately perhaps there are equivalents to reefs and sandbars; and our solar system is surrounded by them. Perhaps the fringes of our system are littered with unlucky wrecks and our sun is on their charts as a navigational hazard?

[Colin Robinson]

Another thought on why there maybe an interstellar civilization or several around us but they aren't here. Perhaps their method of interstellar travel is at some level analogous to sailing the oceans before the age of steam in that there are functional equivalents of wind and currents that the vessels follow, creating natural routes for exploration and expansion. Now if Earth isn't along such a route then the aliens might well be unable or unwilling to come here. Alternately perhaps there are equivalents to reefs and sandbars; and our solar system is surrounded by them. Perhaps the fringes of our system are littered with unlucky wrecks and our sun is on their charts as a navigational hazard?

The case of Antarctica is worth thinking about...

Humans seem to have had sea-going vessels of some sort for at least 50 thousand years. Australia has been inhabited that long, and without boats it is hard to imagine how anyone got here.

Yet the first known sightings of Antarctica occurred less than 200 years ago.... That means that for at least 99.6 percent of the history of human seafaring, one whole continent remained not only uncolonized, not only unexplored, but actually unnoticed.

[baric]

Yet the first known sightings of Antarctica occurred less than 200 years ago.... That means that for at least 99.6 percent of the history of human seafaring, one whole continent remained not only uncolonized, not only unexplored, but actually unnoticed.

Interestingly, the last non-cold landmass colonized by humans was Madagascar.

[hiyatran]

if only we can roam around area 51 freely, maybe we would know if there's such a thing as ET

[baric]

if only we can roam around area 51 freely, maybe we would know if there's such a thing as ET

On the off-chance that you are serious, there's no ET at Area 51. None. Nada. Zero. Zip.

[Garrison]

On the off-chance that you are serious, there's no ET at Area 51. None. Nada. Zero. Zip.

Of course not; he went on the run with Simon Pegg and Nick Frost.

Paul (http://www.whatispaul.com/)

Or possibly he is living with Stan Smith (http://en.wikipedia.org/wiki/American_Dad!). :)

[CaptainToonces]

Humans seem to have had sea-going vessels of some sort for at least 50 thousand years. Australia has been inhabited that long, and without boats it is hard to imagine how anyone got here.
Are you seriously suggesting the colonization of Australia as proof that humans have had ocean-going vessels for 50,000 years? In the last ice age australia was practically connected to southeast asia by land. It's a lot different journey than the one to Antartica.

[Evan]

Naturally I haven't read all 500+ replies. However, the beginning and the tail of this thread do not differ greatly.

Evidence for life elsewhere is not mounting. We don't even have evidence for how life began here. We have many assumptions, wild guesses and informed speculation but we have no idea what the initial conditions were here on Earth that led to the chance occurrence of a self organizing and self replicating organism. Without even that basic knowledge we don't know what to look for elsewhere. We can be reasonably certain that the early atmosphere on Earth wasn't anything like it is today. Free oxygen doesn't hang around for very long without life to replenish it.

The life forms that exist here today are those that have adapted to current conditions. There is also a very large element of pure luck that allowed some types to survive purely by chance when great extinction events occurred. A life form cannot evolve to survive an extinction event nor can it adapt in just a few generations or even a few thousand to survive conditions that are deadly. We do have evidence that a majority of the life forms that existed previously on Earth have failed to survive. The remains of the creatures that are found in the Burgess Shales represent forms of life that were utterly wiped out. They have no present day descendants, nothing that can in any way be reasonably connected to the forms that existed before the event that finished them.

We are lucky that we live in a quiet corner of the galaxy. Of course if we didn't we wouldn't be be here. What is becoming apparent is that galaxies are high energy neighbourhoods and that isn't good news for self organizing, complex anythings. Energetic events have a strong ability to tear things apart. Huge swaths of any galaxy are off limits to anything that depends on persistent structure and organization. High energy environments are inimical to what we consider to be life. Even life that we might not recognize is not exempt from the intensely disordering effects of high energy processes. Wide spectrum high level electromagnetic radiation will disrupt even basic organic molecules as well as inorganic molecules.

This is something for which we are rapidly developing evidence. A black holes forms at the centre of every galaxy and infalling matter spews intense radiation like a Flash Gordon death ray. There is no chance for life to develop, let alone survive, anywhere near the central regions of a galaxy. The Drake Equation needs a few more terms to accurately describe what we now know about our universe. Those terms are essentially negative constants that reduce the probability of life surviving long enough to be noticed. The terms need to include the chances of various extinction events occurring to any particular planet that might give rise to a life form. Everything from simple asteroid impacts to hyper novas in the neighbourhood represent terminal events. Put even weak wild guesses into the equation and what comes out can easily be a negative chance of life developing in any particular galaxy, never mind lasting long enough to develop to a sentient level.

On top of all that we have no idea what it takes for life to go from a self replicating organic soup to something that is able to contemplate that process.

[baric]

We don't even have evidence for how life began here.

I stopped reading right there.

[CaptainToonces]

On top of all that we have no idea what it takes for life to go from a self replicating organic soup to something that is able to contemplate that process.
Actually we have a pretty good idea of one example of that, it's called the history of the Earth. And in fact we don't know the history of any other planets in the universe nearly as well so it's difficult to speculate what they might be like, but why should this one be so rare...

You said that adding the chances of extinction events to the drake equation could give negative chances of life developing in a galaxy. That is false, as that equation cannot mathematically produce a "negative chance". Chances just get closer to 0.

No extinction event has ever wiped out life on Earth, just decimated it.

As far as I know studies have shown that if you take a planet like Earth, in the goldilocks zone where water is liquid, there's a high chance of self-replicating organic soup.

[Evan]

I stopped reading right there.


Why? Perhaps you assumed something you shouldn't? If you think we have evidence for how life began on this planet how about detailing the steps at the biochemical level. I'll wait. A good place to start is with explaining the self organization of a complex chemical structure. We have very little clue how that works and we cannot replicate it at this time. The next hurdle in explaining it is to demonstrate how a self organizing structure can then self replicate a nearly perfect copy of itself.

As to my statement "We don't even have evidence for how life began here.", how about refuting it if you can? Last time I checked there isn't a shred of evidence existing from the time of the origin of life on this world. We don't even have a good handle on when that was.

[Evan]

No extinction event has ever wiped out life on Earth, just decimated it.



Oh? How do you know that? How many times has life restarted on this planet?


As far as I know studies have shown that if you take a planet like Earth, in the goldilocks zone where water is liquid, there's a high chance of self-replicating organic soup.

Apparently not all that high or we would have already done it.

[IsaacKuo]

Oh? How do you know that? How many times has life restarted on this planet?
The fossil record goes back at least 2.7 billion years and perhaps 3.5 billion years. That leaves perhaps a billion years or so before that in which it's possible there was life on Earth which was completely wiped out.

In particular, it's plausible that the Late Heavy Bombardment may have wiped out all life on Earth (if any existed at the time). If so, then it must be very easy for abiogenesis to occur quickly since we have fossil evidence of life so shortly afterward. On the other hand, it's plausible that life may have survived through the Late Heavy Bombardment.

[baric]

Why? Perhaps you assumed something you shouldn't?

Because it ignores 150 years of biological study? It's a blatantly incorrect assertion.

[Evan]

Pure speculation does not constitute evidence. The point is that we have no evidence that explains how life began. There are plenty of guesses that are based on a stack of assumptions bolstered by some serious hand waving, but there is no evidence. We do not know how life began and we may never know. There is nothing left of that time to examine and even if there were it is unlikely that they earliest living organism would leave anything permanent behind when disincorporated for any reason. It is impossible to give any sort of reasonable account of the origin of life on Earth without invoking speculation and assumptions. Since we live here and have direct access to the existing natural history of this planet but cannot determine these factors we are clearly not in a position to establish the parameters of what actually constitutes an exo-world suitable for the origin of life. We can safely say what it takes to support life now but that isn't the same thing. Since we don't know the conditions on this planet at the time life began and succeeded in staying alive we don't know what we are looking for. In particular, what was the constitution of the early atmosphere of Earth? That is directly relevant to recognizing an "Earth like" planet since it is one of the few parameters that we may be able to acertain in the near future.

[Evan]

Because it ignores 150 years of biological study? It's a blatantly incorrect assertion.

Please reread my statement. "We don't even have evidence for how life began here."

What evidence do we have for the process that resulted in the origin of life? We have not accomplished it and we haven't observed it. I have yet to see a detailed description of how it works.

[baric]

Pure speculation does not constitute evidence. The point is that we have no evidence that explains how life began.

This is a classic moving of the goalposts that is similar to the "god of the gaps" arguments in theological discussions.

We have a tremendous amount of evidence about the origin of life on this planet. Just two centuries ago, there was no concept of common descent -- most people assumed divine creation.

Since then, we have learned:
1) Man shares a common ancestor with apes
2) Hominids share a common ancestor with all mammals
3) ALL LIVING CREATURES share a common ancestor

We have discovered the inner workings of the cell and the function of mitochondria and ATP for energy. We have discovered DNA and how it creates variation through generations.

We have sequenced the DNA of bacteria to understand the effects of genes and proteins (way over my head at this point). We have learned enough to refute the "irreducible complexity" arguments about bacterial flagella.

We have literally pushed our understanding about the creation of life on this planet all of the way back to the level of RNA, proteins and genes.

On the other end, from the ground up, we have learned about how easily complex hydrocarbons and other necessary components for life are created by purely natural and undirected chemical processes.

Frankly, to dismiss all of that intellectual progress (AND EVIDENCE) with a blanket assertion like "We don't even have evidence for how life began here" makes you look either very uninformed or cynical.

Just because we have not established a 100% chemical trail from cometary ice to functioning biological organisms does not mean we lack evidence.

Is that what you wanted to hear?

[baric]

Please reread my statement. "We don't even have evidence for how life began here."

I'm not playing your goalpost game.

[Evan]

What goalpost game? I haven't changed anything from my original assertion. We do not know how life began on Earth. We have no reason to believe that RNA and DNA that we know now is the same as what the earliest life forms used to encode information about their own structure. It is much more reasonable that such encoding was a product of evolution just as everything else seems to be. It is very important in scientific enquiry to separate what we know from what we believe, assume and speculate to be so.


We have literally pushed our understanding about the creation of life on this planet all of the way back to the level of RNA, proteins and genes.


We have no evidence that those methods were employed by the aboriginal life forms. They MAY be a product of evolution. There is no evidence either way but Occam's razor argues aginst such a high order of complexity for the earliest organisms. To give you some idea of the level of complexity present in current life forms, it has recently been determined just how many proteins take part in a synapse during the forming of a memory. Just one synapse, not an entire complex memory, requires the participation of over 1,400 proteins. That applies to life forms as lowly as Planaria, not just humans.

Please don't use the term "creation". That implies a creator.

[Evan]

I just did a quick check and found that the very oldest DNA ever found is only 419 million years old. That leaves a gap of as much as 3 billion or so years that still needs explaining.

[IsaacKuo]

I just did a quick check and found that the very oldest DNA ever found is only 419 million years old. That leaves a gap of as much as 3 billion or so years that still needs explaining.
Why do you think this?

Note that most of our information about DNA and its historical development comes from analysis of the DNA of living species.

[Canis Lupus]

As far as I know studies have shown that if you take a planet like Earth, in the goldilocks zone where water is liquid, there's a high chance of self-replicating organic soup.

Great. I would be grateful for some links to the studies, however, I am puzzled by the description, "self-replicating organic soup". Maybe the studies can assist.

[baric]

What goalpost game? I haven't changed anything from my original assertion. We do not know how life began on Earth.

That's not what you said, nor what I was objecting to. You said:

""We don't even have evidence for how life began here."

And yes, this is goalpost-shifting whether you realize it or not. There is absolutely no way we will ever know with 100% certainty how life began on Earth since most of that trail is lost in history.

In other words, no matter how much evidence we find about the origins of life on Earth (including what I listed), people will always be able to shift the goalposts back a little further and claim that we don't really know.

This is logically no less flawed than the "god of the gaps" argument or the neverending search for the missing evolutionary link.

[CaptainToonces]

Great. I would be grateful for some links to the studies, however, I am puzzled by the description, "self-replicating organic soup". Maybe the studies can assist.

Here ya go:
http://en.wikipedia.org/wiki/Origin_of_life#.22Primordial_soup.22_theory

Miller-Urey: http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment

Why is it so hard to believe that if you take a water world with carbon, nitrogen, etc. and add millions of years and sunlight that "life" wouldn't explode all over it?

[Evan]

This is logically no less flawed than the "god of the gaps" argument or the neverending search for the missing evolutionary link.


Hardly. My original statement stands. It is very relevant to finding other worlds that might harbor life since whe need to know what to look for. Looking is our only option and the only tool available in the forseeable future will be to identify something in the spectra of exoplanets that unambiguously points to a living process. Free oxygen is a very good indicator since it has a very short lifetime if it isn't replenished by life forms here on Earth. However, if we are limited to looking only for planets that have free oxygen we may be limiting our search to a very small percentage of the planets that bear life.

What about the early protolife on Earth? It didn't use a metabolic cycle that depended on free oxygen, we can be sure of that much. The Earth would have been very chemically active in the early phases of the development of life and the metabolic cycles that the vast majority of life now on Earth depend on would not have been possible. Some other energy cycle must have been available and some other metabolic side product might be detectable in the atmosphere of such a planet. Knowing what to look for might expand the possiblities by orders of magnitude if life is routinely wiped out by the very nature of the galaxies we live in. Right now we do not know what to look for since we do not know the early history of life on this planet.

It isn't a question of moving goalposts. The identification of proto life depends on us knowing how it works.

[CaptainToonces]

Oh? How do you know that? How many times has life restarted on this planet?
I doubt it has ever had to restart once it got started. When you do your dishes do you think that you eradicate every last bacterium on them?

I will grant you that there may be some events that can happen over 4 billion years to completely sterilize a life planet but these are not on the order of asteroid impacts we have endured here. Such events would have to be planet-planet collisions or some such amazingly destructive event it would take to really kill off 100% of the bacteria here.

[Canis Lupus]

Perhaps it's a differing level of evidence which an individual will be satisfied with which is causing the disagreement. Some are content with a sketchy picture as being ample enough evidence, while others want something more exact.

As has been stated, it may well be impossible to determine how life started on Earth, but if experiments attempting to produce life through abiogenesis are successful, we'd have a fairly strong indicator. Until then, or until some other observation indicates another source, I would have to agree with Evan that "we don't have evidence for how life began here", although we do have ample evidence that life has begun here. Obviously, it would be a good idea for further and on-going enquiry not to confuse the two.

In relation to moving goal posts, which can be quite frustrating during discussion, even allowing for the inevitable refinement of positions which occur during fruitful discussions, lumbering someone with a 100% certainty requirement seems quite a shift. Did Evan ever require such a thing?

[Evan]

Why is it so hard to believe that if you take a water world with carbon, nitrogen, etc. and add millions of years and sunlight that "life" wouldn't explode all over it?

It isn't particularly hard to believe until you look at the details. That early world may not have much sunlight at the surface. It probably had continuous acid rain from high levels of sulphur in the atmosphere. Ionizing radiation background levels would be many times higher than the are now. Instead of conditions being especially favorable they may have been especially unfavorable with the result that life has only a slim chance of getting going on a permanent basis. Living forms are demonstrably easy to kill. Current life forms cannot tolerate very much variation in conditions. There are only a very few exceptions to that general principle and they are all very low level forms of life such as Radiodurans. The fact that Radiodurans is still here suggests that it was an evolutionary dead end but it also suggests that conditions were much more hostile than we suspect.

I counter with another question. Why is it so hard to believe that high energy events which demonstrably exist in abundance would wipe out most of the life that does manage to get started?

I must go to town so I will check back this evening.

[Canis Lupus]

Here ya go:
http://en.wikipedia.org/wiki/Origin_of_life#.22Primordial_soup.22_theory

Miller-Urey: http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment

Why is it so hard to believe that if you take a water world with carbon, nitrogen, etc. and add millions of years and sunlight that "life" wouldn't explode all over it?

I may have missed some detail but I found no reference to anything "self-replicating" in the linked to wiki entry about the study.

[CaptainToonces]

I counter with another question. Why is it so hard to believe that high energy events which demonstrably exist in abundance would wipe out most of the life that does manage to get started?
Well, because that's not what we observe in the fossil record, and it doesn't make common sense either. The fossil record shows that even the worst extinction events here have reduced the biodiversity of species, but have not come close to threatening the existence of life on Earth (http://en.wikipedia.org/wiki/Extinction_event).

Common sense tells you what i said with my dish washing analogy. You can subject that dish to all sorts of bleach, boiling water, radiation, whatever, and one lucky bacterium out of the millions on there is going to find a protected crevice and survive.

[baric]

Hardly. My original statement stands. It is very relevant to finding other worlds that might harbor life since whe need to know what to look for. Looking is our only option and the only tool available in the forseeable future will be to identify something in the spectra of exoplanets that unambiguously points to a living process. Free oxygen is a very good indicator since it has a very short lifetime if it isn't replenished by life forms here on Earth. However, if we are limited to looking only for planets that have free oxygen we may be limiting our search to a very small percentage of the planets that bear life.

What about the early protolife on Earth? It didn't use a metabolic cycle that depended on free oxygen, we can be sure of that much. The Earth would have been very chemically active in the early phases of the development of life and the metabolic cycles that the vast majority of life now on Earth depend on would not have been possible. Some other energy cycle must have been available and some other metabolic side product might be detectable in the atmosphere of such a planet. Knowing what to look for might expand the possiblities by orders of magnitude if life is routinely wiped out by the very nature of the galaxies we live in. Right now we do not know what to look for since we do not know the early history of life on this planet.

It isn't a question of moving goalposts. The identification of proto life depends on us knowing how it works.

What cracks me up about your insistence that we don't have evidence of how life arose is that you rely on such evidence to make your case.

How exactly can you make authoritative statements about the metabolic cycle of protolife on Earth? Why are you so sure about what is likely or not likely? Are you just pulling those arguments out of thin air or are they based on evidence gathered about the inner workings of the simplest forms of life on this planet?

[KABOOM]

Naturally I haven't read all 500+ replies. However, the beginning and the tail of this thread do not differ greatly.

Evidence for life elsewhere is not mounting. We don't even have evidence for how life began here. We have many assumptions, wild guesses and informed speculation but we have no idea what the initial conditions were here on Earth that led to the chance occurrence of a self organizing and self replicating organism. Without even that basic knowledge we don't know what to look for elsewhere. We can be reasonably certain that the early atmosphere on Earth wasn't anything like it is today. Free oxygen doesn't hang around for very long without life to replenish it.

The life forms that exist here today are those that have adapted to current conditions. There is also a very large element of pure luck that allowed some types to survive purely by chance when great extinction events occurred. A life form cannot evolve to survive an extinction event nor can it adapt in just a few generations or even a few thousand to survive conditions that are deadly. We do have evidence that a majority of the life forms that existed previously on Earth have failed to survive. The remains of the creatures that are found in the Burgess Shales represent forms of life that were utterly wiped out. They have no present day descendants, nothing that can in any way be reasonably connected to the forms that existed before the event that finished them.

We are lucky that we live in a quiet corner of the galaxy. Of course if we didn't we wouldn't be be here. What is becoming apparent is that galaxies are high energy neighbourhoods and that isn't good news for self organizing, complex anythings. Energetic events have a strong ability to tear things apart. Huge swaths of any galaxy are off limits to anything that depends on persistent structure and organization. High energy environments are inimical to what we consider to be life. Even life that we might not recognize is not exempt from the intensely disordering effects of high energy processes. Wide spectrum high level electromagnetic radiation will disrupt even basic organic molecules as well as inorganic molecules.

This is something for which we are rapidly developing evidence. A black holes forms at the centre of every galaxy and infalling matter spews intense radiation like a Flash Gordon death ray. There is no chance for life to develop, let alone survive, anywhere near the central regions of a galaxy. The Drake Equation needs a few more terms to accurately describe what we now know about our universe. Those terms are essentially negative constants that reduce the probability of life surviving long enough to be noticed. The terms need to include the chances of various extinction events occurring to any particular planet that might give rise to a life form. Everything from simple asteroid impacts to hyper novas in the neighbourhood represent terminal events. Put even weak wild guesses into the equation and what comes out can easily be a negative chance of life developing in any particular galaxy, never mind lasting long enough to develop to a sentient level.

On top of all that we have no idea what it takes for life to go from a self replicating organic soup to something that is able to contemplate that process.


I find your thought process to be very inconsistent. While you (properly) caution on numerous fronts that we have "no evidence" with respect to life other than on Earth, you state other equally speculative opinions as if they were facts.

"the chance occurrence" of a replicating system starting on Earth, implies it was a long shot or blind luck. You, nor anyone else, know this. The right conditions in the GZ for enough time may result in life virtually all of the time or only 1 in a billion. There is no hard evidence towards either end of the spectrum.

Similarly, your statement of fact that it was pure "random luck" as to which species survived extinction events. Enough to refill every diverse inhabitable niche on the planet at least twice.

Similarly, your statments of "fact" that life can only survive on the outer fringes of a galaxy.

[Canis Lupus]

Well, because that's not what we observe in the fossil record, and it doesn't make common sense either. The fossil record shows that even the worst extinction events here have reduced the biodiversity of species, but have not come close to threatening the existence of life on Earth (http://en.wikipedia.org/wiki/Extinction_event).

Common sense tells you what i said with my dish washing analogy. You can subject that dish to all sorts of bleach, boiling water, radiation, whatever, and one lucky bacterium out of the millions on there is going to find a protected crevice and survive.

Didn't Evan use the phrase "most of life", yet your post appears to be addressing the idea of "all of life". You seem to be arguing with your own idea, not someone else's.




I counter with another question. Why is it so hard to believe that high energy events which demonstrably exist in abundance would wipe out most of the life that does manage to get started?

[CaptainToonces]

Canis, I took his "most" in that statement to refer to "most of the planets in the galaxy where life gets started are fully sterilized by extinction events." Perhaps I misinterpreted his meaning, or perhaps you did. Either way, he is arguing that the events we refer to as extinction events are responsible for the Fermi paradox which is not true, because life on the Earth, for example, recovered rather quickly from these events and was never really threatened by them.

Now, there could be longer-term sterilization events, such as what presumably happened with Mars losing its atmosphere for lack of a magnetic field.

[eburacum45]

I broadly agree with Evan in that it may never be possible to pin down exactly how life started on Earth. Perhaps the only way to do that with any certainty is to find a broad cross-section of young Earth-like planets in various stages of development, and find out what stage (if any) abiogenesis has reached on each of them. This might give a good indication of how life started on our own planet.

Or, quite possibly it may not. It may be the case that there are several routes to abiogenesis, and the Early Earth might have supported more than one of them; if (by any chance) the end results are reasonably similar, we may never know exactly which route to abiogenesis was followed by the Early Earth. After examining many Earth-like worlds in detail and replicating the various processes in the lab, there still may be some doubt in this field.

[Canis Lupus]

Canis, I took his "most" in that statement to refer to "most of the planets in the galaxy where life gets started are fully sterilized by extinction events." Perhaps I misinterpreted his meaning, or perhaps you did. Either way, he is arguing that the events we refer to as extinction events are responsible for the Fermi paradox which is not true, because life on the Earth, for example, recovered rather quickly from these events and was never really threatened by them.

Now, there could be longer-term sterilization events, such as what presumably happened with Mars losing its atmosphere for lack of a magnetic field.

Yep, your interpretation is more consistent with his original post.

[Luckmeister]

Here's an interesting interview (http://www.nytimes.com/2010/05/18/science/18conv.html) with Jeffrey L. Bada regarding recent discoveries pertaining to the 1950 Stanley Miller experiments.

[Evan]

What cracks me up about your insistence that we don't have evidence of how life arose is that you rely on such evidence to make your case.

I'm not making a case for anything. The case that needs to be made is to show how life arose. That hasn't been done. We don't have a clue either.

Anyway, I have a couple of minutes to spare before I leave for town so I though I would post some of my artwork that bears directly on this question.

This is the usual image that is put forth when the evolutionary beginnings of life are taught and discussed. A pleasant looking place with everything "Just Right" as per the Goldilocks reference so often used. How could anyone dare to doubt that life couldn't help but arise in such an idyllic looking place?

http://ixian.ca/astro/protoearth1.jpg

This however is a much more realistic situation. Heavy clouds even on a "sunny" day and the sun turned orange by volcanic plumes high in the stratosphere. A landscape coloured red from the constant generation of iron oxide as all the traces of of oxygen from arriving comets is consumed. Puddles that are dilute sulphuric acid from that almost continuous rain that washes the sulphur compounds out for the air, placed there by constant volcanism. This isn't how things are now and the way things are now isn't how it was back then.

http://ixian.ca/astro/protoearth2.jpg

[CaptainToonces]

Nice work, Evan!

Certainly the conditions were different then, but it is still made up of the same building blocks of carbon, nitrogen, water, etc.. The place is being pumped with energy from the Sun every day, why wouldn't repetitive processes begin to take hold?

[MaDeR]

First things first: "warm pond" idea is very old hat. For some time more exotic places are accepted as plausible start of life by sciencists, like hydrothermal wents (http://en.wikipedia.org/wiki/Hydrothermal_vent).


way things are now isn't how it was back then.
Yes, exactly. Today, abiogenesis on Earth is impossible - anything that could potentially start selfreplicating will be eaten by someone as free lunch long, long before anything interesting occurs.

[astromark]

All very interesting with points to be made for both sides of this argument.. and then I read that the 'Late bombardment' may have not endangered or destroyed but instead seeded life here.. This argument is equally difficult to refute without a great deal of information. Information that seems to be hard to find. However it should be noted that on this planet there is a abundance of life.. We know that stars just like our Sun are common. Given the Goldilocks zone and the elements required...Seems to me its just a mater of time., and timing. Evidence for ET might not be mounting... but our knowledge of methods for finding it are...

[Colin Robinson]

Are you seriously suggesting the colonization of Australia as proof that humans have had ocean-going vessels for 50,000 years? In the last ice age australia was practically connected to southeast asia by land.

Of course there was less sea between Australia and South East Asia in the last ice age than today. However, the Wikipedia article "Early Human Migrations", mentions "gaps... at least 90 km wide, indicating that settlers had knowledge of seafaring skills".
http://en.wikipedia.org/wiki/Early_human_migrations#South_Asia_and_Australia

Note that Australia remained zoologically distinct from other continents. Apart from humans, there were no placental mammals except those that could swim through the ocean (seals) or fly across it (bats). (The dingo dog arrived later, and apparently by boat.)


It's a lot different journey than the one to Antartica.

A different sort of journey, yes, but a sea journey all the same. Just as sending human beings to another star would be a very different proposition than those trips to the moon. Even though, like the moon journeys, it would be a sort of space flight...

[Evan]

The place is being pumped with energy from the Sun every day, why wouldn't repetitive processes begin to take hold?

They most certainly did unless you want to posit panspermia. The question is what sort. Evolution had a very long time to select for life forms that were the most successful at taking advantage both of changing conditions and being able to pass along the encoded information to sucessors. It think (opinion) that the present method of encoding using RNA and DNA were relatively late developments. It's a very complex system that didn't just automatically spring into existence. To postulate that DNA was there from the beginning tends to require that it formed first and then accidentally put together sequences that caused the assembly of proteins that could provide such things as protective containers for the DNA. DNA is very easy to destroy so that postulate doesn't make much sense. The converse requires the development of protective containers for something that doesn't exist and with no means to pass on the hard coded instructions to make itself.

The answer is not at hand but we need it to find possible life bearing planets that aren't sending I Love Lucy at us. If we can pin down what sort of metabolic process is the most likely then we may have a chance of finding something in the spectra of such planets. We are finally arriving at the point where our detection methods are no longer selecting for giant planets. From here on we will be building a catalogue of places to check when the necessary equipment to capture a spectrum of light reflected from the upper atmosphere has a chance of giving up some information.

[Colin Robinson]

This however is a much more realistic situation. Heavy clouds even on a "sunny" day and the sun turned orange by volcanic plumes high in the stratosphere. A landscape coloured red...

Your picture of primordial Earth reminds me of artists' impressions of the surface of Titan today. Which makes sense, because Titan and ancient Earth have quite a few things in common.


Free oxygen is a very good indicator since it has a very short lifetime if it isn't replenished by life forms here on Earth. However, if we are limited to looking only for planets that have free oxygen we may be limiting our search to a very small percentage of the planets that bear life.
What about the early protolife on Earth? It didn't use a metabolic cycle that depended on free oxygen, we can be sure of that much...

The relation between oxygen and life is an interesting question, and one on which quite a lot of scientific work has been done.

A range of experiments have been done to see how complex carbon compounds could have formed on ancient earth; both before and after the famous one by Urey and Miller.

One basic finding is that it just doesn't work if there is too much oxygen/too little hydrogen in the ingredients. "...as soon as the net conditions become oxidizing, the organic synthesis effectively turns off". (Quote from the book Intelligent Life in the Universe, by I.S.Shklovskii and Carl Sagan)

In short, even though some living things on Earth now do have a use for that oxygen stuff, it is just as well there wasn't too much of the stuff around when life was getting started, because otherwise life here probably wouldn't have started at all.

Even on earth today there are organisms (known as anaerobes) which don't need free oxygen, and in some cases can't function in its presence. Some of these organisms may be dependent on oxygen-breathers for fuel, but others are not, e.g. there are some which get their energy by reacting hydrogen with carbon dioxide.


Some other energy cycle must have been available and some other metabolic side product might be detectable in the atmosphere of such a planet.

Are you aware of the hypothesis that organisms on the surface of Titan obtain energy by combining hydrogen with compounds such acetylene and ethane to produce methane?

Which indeed would constitute an energy cycle, because in Titan's upper atmosphere, the opposite reactions are known to occur, with the help of energy from the sun: methane gets converted into compounds such as acetylene and ethane, with release of hydrogen.

Such a cycle might indeed produce detectable chemical anomalies in an atmosphere: exactly the sort of anomalies reported for Titan in June last year.

Then again, chemical anomalies may indicate nothing more than anomalous chemistry. We won't know for sure till we get a closer look.

[Evan]

Are you aware of the hypothesis that organisms on the surface of Titan obtain energy by combining hydrogen with compounds such acetylene and ethane to produce methane?


Yes. The catch to that hypothesis is the temperature and the rate at which the reaction would proceed, or not proceed. Not much happens chemically at the temperature of liquid nitrogen. There isn't a steep enough energy gradient to drive local entropy down. As for anomalous chemistry, that reminds me of the initial findings of the Viking Landers on Mars. They detected something that wasn't expected but the experiments weren't sophisticated enough to indicate what was driving the reactions. As it turned out it was simply inorganic materials with a lot of dangling bonds and no oxygen to fill them. Many if not most of the light elements are extremely active and when irradiated they become much more so. Still, at 97K even normally energetic reactions are hard to initiate.

One argument posits "so what?", the reactions will just proceed more slowly. While that is partly true life as we know it doesn't just depend on a single simple chemical reaction such as the Krebs cycle. There is a very long list of reactions that all must be operational for our form of life to work. When the temperature is reduced that far many of the reactions come to a full stop. Others may proceed at a very, very slow pace but the reaction time differences for various reaction cycles are highly exaggerated as the temperature falls. That can cause sequences to fail even though all of the parts of a cycle are able to proceed individually.

A common objection to analysis such as this is to simply state that we don't know everything there is to know about how life might form (and be powered). While that is most certainly true there are some fairly strict limitations imposed by physics that apply everywhere regardless of what might be possible when considered in isolation.

[KABOOM]

Yes. The catch to that hypothesis is the temperature and the rate at which the reaction would proceed, or not proceed. Not much happens chemically at the temperature of liquid nitrogen. There isn't a steep enough energy gradient to drive local entropy down. As for anomalous chemistry, that reminds me of the initial findings of the Viking Landers on Mars. They detected something that wasn't expected but the experiments weren't sophisticated enough to indicate what was driving the reactions. As it turned out it was simply inorganic materials with a lot of dangling bonds and no oxygen to fill them. Many if not most of the light elements are extremely active and when irradiated they become much more so. Still, at 97K even normally energetic reactions are hard to initiate.

One argument posits "so what?", the reactions will just proceed more slowly. While that is partly true life as we know it doesn't just depend on a single simple chemical reaction such as the Krebs cycle. There is a very long list of reactions that all must be operational for our form of life to work. When the temperature is reduced that far many of the reactions come to a full stop. Others may proceed at a very, very slow pace but the reaction time differences for various reaction cycles are highly exaggerated as the temperature falls. That can cause sequences to fail even though all of the parts of a cycle are able to proceed individually.

A common objection to analysis such as this is to simply state that we don't know everything there is to know about how life might form (and be powered). While that is most certainly true there are some fairly strict limitations imposed by physics that apply everywhere regardless of what might be possible when considered in isolation.

How will these "reactions" play out, several billion years in the future whence Sol is in the midst of its Red Giant phase and tempartures on Mars/Titan have risen?

[Colin Robinson]

Yes. The catch to that hypothesis is the temperature and the rate at which the reaction would proceed, or not proceed. Not much happens chemically at the temperature of liquid nitrogen. There isn't a steep enough energy gradient to drive local entropy down.

The point about temperature and chemical reactivity is an important one.

Although Titan is not at "the temperature of liquid nitrogen" -- the nitrogen there is actually a gas, as on Earth. Nitrogen-rich atmosphere is one of the things Titan and Earth have in common.

If life isn't happening on Titan, then what is happening? It has been established that many different carbon-chain molecules are generated in the upper atmosphere by the action of UV radiation on methane. So what happens to those carbon-chain molecules? Do they sink to the surface and accumulate there, and if so in what form? (Before Cassini-Huygens got there, people were expecting a deep global hydrocarbon ocean, which is not what was found.) Or do they eventually break down chemically, absorbing hydrogen, and turn back into methane? According to Chris McKay, who is a specialist in this area, such a reaction couldn't happen without a catalyst, and no-one knows what sort of catalyst would work. As you've just mentioned, it's more difficult for chemistry to happen at low temperatures...

So what is going on?

[marsbug]

One of the intruiging ideas that is often raised in discussions about the nature and definition of 'life' is that very complex chemistry, even with unpredictable emergent properties and behavoirs we would normally associate with life, does not have to be life.... at least by any standard the scientific mainstream would agree on.

This thought might well be very applicable to Titan - chemical bonds that are unstable or metastable here would be rock solid there. Bonds that can only exist for fractions of a second here could well be at least be metastable there. The most abundant solvents are not polar and are themselves organic molecules - and our robots could labour on the surface for decades without catalouging all the chemical species on its surface, near subsurface, and atmosphere. Then there are going to be traces of more Earth like chemistry left over from events that warm the ice surface to melting briefly, like large asteroid strikes.
Titan is a wholly different game to Earth, and 'whats going on' could be almost as complex as living chemistry without having life.

There are lots of mysteries - my favorite are why the lakes seem to be so flat: Is that telling us that they are not just methane and ethane but a more complex mix with a much higher viscosicity? But its fun to speculate about what could be happening in the upper atmosphere to - thats where the energy is, thats where the chemistry moves fastest. Anyone fancy writing to their space agency and asking for a Titan sample return? :D

Its a great pity that it'll be decades before we go back.

[CaptainToonces]

The definition of life seems rather vague to me. Even if there is some agreed upon set of criteria that some learned society has agreed upon, that is just one definition. We see a wide variety of environments just in our solar system alone. What's going on on Earth happens to have resulted in some assemblages of energy that are so clever at surviving they are aware they're doing it. I guess we call that life, but is it that much more special than the chemistry of any other planet?

[Trakar]

The definition of life seems rather vague to me. Even if there is some agreed upon set of criteria that some learned society has agreed upon, that is just one definition. We see a wide variety of environments just in our solar system alone. What's going on on Earth happens to have resulted in some assemblages of energy that are so clever at surviving they are aware they're doing it. I guess we call that life, but is it that much more special than the chemistry of any other planet?

Apparently, ...so far.

[Colin Robinson]

One of the intruiging ideas that is often raised in discussions about the nature and definition of 'life' is that very complex chemistry, even with unpredictable emergent properties and behavoirs we would normally associate with life, does not have to be life.... Titan is a wholly different game to Earth, and 'whats going on' could be almost as complex as living chemistry without having life.

In that case, Titan might be able to enrich our understanding of life on Earth, and provide clues to what may be happening elsewhere in the universe, even if it turns out not to have life as such.


Anyone fancy writing to their space agency and asking for a Titan sample return? :D

For a space agency that wants scientific results, I think another mission to Titan would be an excellent investment. It wouldn't need to be able to return samples to Earth, as long as it could land, move about, use something like a gas chromatograph/mass spectrometer to analyse chemical compositions of soil, liquid and atmosphere samples; and use a microscope to send back photographs at various levels of magnification. The microscope could give us more information about the crystalline structure of icy precipitates, and could also identify tiny aggregrations of organic substances... which might or might not be living ET cells.

[astromark]

Its interesting and a long way from the OP... Considerable discussion about all the unknowns of this subject could fill books and does. Why any one thinks we can come in here and say such a few things and expect any agreement is facing disappointment.

Not that any point of view is wrong. It most likely is not. Its just that the variables are so many and so large...
Without a case to study we can not hope to be precise and accurate. This is information we just do not have yet...

[Evan]

Physics does impose constraints on the forms that life may take. The constraints aren't absolute but in evolutionary terms they are very strong. The carbon cycle that we use, and that nearly all life forms on Earth use is the most efficient and provides the most bang for buck of any that we know about. Others are possible and examples exist but none approach the specific energy content per units of mass as well as the controllability etc. of the carbon cycle. We can be confident that life at only slighly higher temperatures isn't possible if it involves the most common organic molecules. The question of life using similar reactions at much lower temperatures might have a slight crack that can be pried open but we certainly don't have any evidence for it or a good working hypothesis of how it might function. I think (opinion) it's a pretty safe bet that life elsewhere will resemble life here. That said, we need to know what life here resembled for what was probably a large percentage of the time life has existed here.

Funding should be provided to the end of determining just what forms of life might have begun the evolutionary sequence on Earth. If we can come up with reasonable answers to that question the chances of finding life elsewhere would be greatly improved.

[Colin Robinson]

The definition of life seems rather vague to me. Even if there is some agreed upon set of criteria that some learned society has agreed upon, that is just one definition. We see a wide variety of environments just in our solar system alone. What's going on on Earth happens to have resulted in some assemblages of energy that are so clever at surviving they are aware they're doing it. I guess we call that life, but is it that much more special than the chemistry of any other planet?

One definition of life found in astrobiological literature is "a chemical system capable of Darwinian evolution".
http://books.nap.edu/openbook.php?record_id=11919&page=6

Conceivably, something could fit that definition, yet be chemically quite different from Earth life, "life as we know it".

On the other hand, one can imagine chemical systems which in some ways resemble life, yet wouldn't fit the above definition.

For instance, reproduction is one of the defining qualities of life. Yet, there are a number of chemicals which function as auto-catalysts, that is, chemical A prompts chemicals B and C to combine into more of A. I was surprised to read that autocatalysts include molecules as simple as formamide (CHONH2) -- it can cause dissolved carbon monoxide (CO) and ammonia (NH3) to combine into more formamide, according to Wikipedia.
http://en.wikipedia.org/wiki/Formamide#Self-replication

But because formamide is so simple, it presumably couldn't actually mutate and evolve like its more complex chemical relatives, RNA and DNA.

All of which make me wonder how we would classify a planet or a moon with an active chemistry involving autocatalysts more complex than formamide, but less complex than RNA? It might be quite difficult to work out whether Darwinian evolution was happening there or not...

[marsbug]

The OP of this thread (http://www.bautforum.com/showthread.php/87734-The-Origin-of-Life-Descent-of-Electrons?highlight=descent+of+electrons) (and resulting discussion) has an interesting take on 'what is life'.

[Infinitenight2093]

http://www.youtube.com/watch?v=rhF4-6i9hR8

excellent news!

[Evan]

But because formamide is so simple, it presumably couldn't actually mutate and evolve like its more complex chemical relatives, RNA and DNA.

All of which make me wonder how we would classify a planet or a moon with an active chemistry involving autocatalysts more complex than formamide, but less complex than RNA? It might be quite difficult to work out whether Darwinian evolution was happening there or not...

Comparing chemical compounds such as formamide (or more complex but similar molecules) to RNA/DNA is really apples and oranges. RNA and DNA are expressly evolved to act as flexible code storage compounds. They are a type of binary code and in fact RNA is just that. The genetic sequence of part of the H1N1 virus contains 8 units that code for infectivity and that produces precisely 256 combinations.

When DNA mutates it is simply rearranged to form a different code. Because of it's extreme flexibility in how the amino acids may be combined it isn't considered to be a different molecule even when the sequence is different. It's a very special case compared to simple molecules. Change the structure of a simple molecule and you have a different substance with sometimes radically different properties. That can't be considered a mutation but instead the product of some sort of reaction. Also, in the case of a self catalyzing reaction any change to the molecule will bring it to a halt or entirely change the nature of the reaction. Even racemic differences will have that effect. That doesn't fit the description of evolutionary mutations. To be considered as a part of a living organism the coding system must carry the information to build the organism which it then uses as direct instructions to automatically assemble raw materials into coherent functional assemblies. Those assemblies then function to both protect and to provide the DNA with the enviroment it requires to produce more of those assemblies. Basically, the reason we have a mouth etc is to make more DNA. I think that is a pretty good description of life regardless of the chemistry it may use.

DNA isn't alive by itself since it cannot replicate without the structure that it produced to enable it to reproduce. As I alluded earlier this is very much a chicken/egg situation. How does a cell evolve an information /replication system without an information /replication system to produce the cell?

[Colin Robinson]

The question of life using similar reactions at much lower temperatures might have a slight crack that can be pried open but we certainly don't have any evidence for it

What sort of evidence would you expect a population of low temperature microbes to provide?

To put the question another way: How would you expect a Titan without low temperature microbial life to differ from a Titan with abundant microbial life?

[Colin Robinson]

The OP of this thread (http://www.bautforum.com/showthread.php/87734-The-Origin-of-Life-Descent-of-Electrons?highlight=descent+of+electrons) (and resulting discussion) has an interesting take on 'what is life'.

Thank you for this link. I've just read the American Scientist article by James Trefil, Harold Morowitz and Eric Smith
at http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1
which was the starting point of that thread. I would recommend that article to anyone interested in the topic of abiogenesis and in the likelihood of evolution getting started on many worlds.

[Evan]

What sort of evidence would you expect a population of low temperature microbes to provide?

To put the question another way: How would you expect a Titan without low temperature microbial life to differ from a Titan with abundant microbial life?

Without a proposed chemical cycle of equivalent complexity to the simplest ones found here that question cannot be aswered. I personally don't think that life on Titan is possible. I haven't seen anything put forth other than a lot of handwaving that convinces me that the necessary chemical reactions exist. This isn't that hard to investigate on Earth. Where is the data? I have been a student of science all my life and of chemistry and physics in particular. I have set up many an experiment when I was young for my father in his teaching lab. It is axiomatic that very cold temperatures stop biological processes. If it didn't then why do we freeze biological specimens? Specimens with a room temperature lifetime of minutes can be held for decades at (or near) the temperature of liquid nitrogen.

You can't just slow down a reaction and expect the same result that just takes longer. In most cases you can't slow down a reaction at all. It either proceeds at a certain rate or it doesn't proceed. The best candidates for reactions that migh occur at 97K are those that take place one molecule at a time independent of the presence of nearby molecules. That, unfortunately isn't how life works around here. Reactions occur in bulk, not just a few atoms at a time. Even something the size of a bacterium has "bulk" reactions going on. E-coli is mader from about 100 billion atoms.

The cycle that provides cellular chemical power for earthly aerobic life forms is the Krebs Cycle. It isn't simple and it demands fairly strict conditions to operate. Even the smallest aerobic bacterium uses this cycle for cellular energy.

http://ixian.ca/astro/krebs.jpg

http://chemwiki.ucdavis.edu/Biological_Chemistry/Metabolism/Kreb's_Cycle
Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License

[Colin Robinson]

It is axiomatic that very cold temperatures stop biological processes. If it didn't then why do we freeze biological specimens? Specimens with a room temperature lifetime of minutes can be held for decades at (or near) the temperature of liquid nitrogen.

Organisms on Earth use liquid water as a solvent in which to do their chemistry. If you freeze their water, they stop functioning. The question is whether another liquid, with a different freezing point, may be used as a solvent by organisms elsewhere.


Without a proposed chemical cycle of equivalent complexity to the simplest ones found here that question cannot be aswered. I personally don't think that life on Titan is possible. I haven't seen anything put forth other than a lot of handwaving that convinces me that the necessary chemical reactions exist. This isn't that hard to investigate on Earth.

As the astrobiologist David Grinspoon says:

"Our knowledge about the potential for organic life came by reverse-engineering life on Earth... I’m not sure we could have learned it if we had to start from principles and try to invent carbon-based life through physics and chemistry, rather than dissecting the example that has been given to us."

http://livingintheuniverse.com/Interviews/grinspoon.html

You want someone to come up with a detailed model of biochemical cycles on Titan, without first having a specimen organism to reverse-engineer? Perhaps someone will. But if it happens, it will not be the same as the way scientists came up with their description of the Krebs cycle.

It isn't that hard, you say. Logically then, would it not be even less hard to come up with a detailed model of Titan's chemistry which does NOT involve life? After all, non-living chemistry is generally rather simpler that living chemistry, isn't it?

[Evan]

You want someone to come up with a detailed model of biochemical cycles on Titan, without first having a specimen organism to reverse-engineer? Perhaps someone will. But if it happens, it will not be the same as the way scientists came up with their description of the Krebs cycle.

Not what I meant. What I want is for someone to come up with a detailed model that can function on Titan even if it doesn't exactly fit the observed evidence so far. We know enough about chemistry to start by easily ruling out a wide range of reactions that won't work. What is left is a very short list and the required conditions are easily duplicated in the lab.

As for explaining what we have observed, we don't have sufficient information about the atmosphere dynamics. The reactions that do occur are almost certainly all taking place where the energy is, at the cloud tops. Even though the ambient temperature is still very low there is plenty of incident radiation to initiate and promote reactions. That is what is missing at the surface. Again, that is quite easy to duplicate in the lab. All it takes is money and that is a political problem.

[IsaacKuo]

I personally don't think that life on Titan is possible.
What about life in Titan? There may be a liquid water ocean underneath the surface of Titan.

[astromark]

What you / we think, is based on what ?
You can see that answering that question sets up a number of different roads to look down.
Until signs of life are detected 'We are pointing in the dark'
Without enlightenment of facts we just do not yet know what we need to.
In science guess work is not acceptable as that what could move our expectations.
We can postulate our expectations and do... But until we send some robotics out there and detect a microbial entity or two.
We are a little stuck. The answer is budgeting.
This subject requires a urgency of increased budgeting or another generation passes without knowing the answer we seek.
Evidence for ET is NOT mounting... It might be that our ability is getting sharper. More refined.
As we have not a single case to study.. Nil is not a increase its a stalemate. Its wishful thinking...

[Evan]

What about life in Titan? There may be a liquid water ocean underneath the surface of Titan.

??? Are you perhaps thinking of Enceladus instead of Titan? Enceladus is thought to have a liquid water ocean beneath the ice.

[Noclevername]

??? Are you perhaps thinking of Enceladus instead of Titan? Enceladus is thought to have a liquid water ocean beneath the ice.

Several ice/rock moons may fit that hypothesis, including Titan and Enceladus.

[Colin Robinson]

Not what I meant. What I want is for someone to come up with a detailed model that can function on Titan even if it doesn't exactly fit the observed evidence so far. We know enough about chemistry to start by easily ruling out a wide range of reactions that won't work. What is left is a very short list and the required conditions are easily duplicated in the lab.

As for explaining what we have observed, we don't have sufficient information about the atmosphere dynamics. The reactions that do occur are almost certainly all taking place where the energy is, at the cloud tops. Even though the ambient temperature is still very low there is plenty of incident radiation to initiate and promote reactions. That is what is missing at the surface.

Are you aware of Darrell Strobel's work regarding the behavior of H2 molecules in Titan's atmosphere? He developed a model, based on computer analysis of data from Cassini-Huygens, where H2 is diffusing downwards through the atmosphere at the net rate of 10 to the power 25 molecules per second. Near the surface it disappears, i.e. it is either taken out of the atmosphere, or it gets incorporated into some other molecule such a methane.

Darrell Strobel is a specialist in this area, who has also written about movement of H2 molecules in the opposite direction: from Titan's upper atmosphere into space. No contradiction there -- the picture that emerges is that H2 molecules are formed in the upper atmosphere, some go up into space, some go down into the lower atmosphere, while others remain more or less where they are.

It's true that Strobel's work about the downward diffusion is quite recent (published June last year), and subject to confirmation etc etc. But, if his model happens to be right, certain conclusions follow...

1. In conjunction with hydrocarbons more complex than methane, H2 is a carrier of chemical energy. Downward flow of H2 molecules through the atmosphere means that energy is getting transferred from the upper regions to the region near the surface.

2. A question to be answered is what happens to the molecules, and to their energy, when they get near the surface. A population of methane-producing organisms is one possible explanation. Other explanations are possible, e.g. a non-living chemistry involving a catalyst.

As far as I know, it is true that we don't have a detailed model of just how Titan organisms would metabolize hydrogen. But neither do we have a detailed model of how a non-living chemistry would convert the hydrogen into something else.


Again, that is quite easy to duplicate in the lab.

I don't know about "quite easy". But certainly researchers have made attempts to simulate Titan conditions in Earth laboratories. For instance, an experiment completed October last year (by Sarah Horst of the University of Arizona) reportedly produced compounds including the five nucleotide bases from a simulation of Titan's upper atmosphere.

No doubt simulation attempts will continue, and I wish the researchers luck...

[marsbug]

Not what I meant. What I want is for someone to come up with a detailed model that can function on Titan even if it doesn't exactly fit the observed evidence so far. We know enough about chemistry to start by easily ruling out a wide range of reactions that won't work. What is left is a very short list and the required conditions are easily duplicated in the lab.

As for explaining what we have observed, we don't have sufficient information about the atmosphere dynamics. The reactions that do occur are almost certainly all taking place where the energy is, at the cloud tops. Even though the ambient temperature is still very low there is plenty of incident radiation to initiate and promote reactions. That is what is missing at the surface. Again, that is quite easy to duplicate in the lab. All it takes is money and that is a political problem.

Thats a good point, and there are efforts underway - check out some of the poster abstracts from LPSC 2011. (http://www.lpi.usra.edu/meetings/lpsc2011/pdf/program.pdf) That said we know so little about Titan any attempt at a 'proof of principle' biochemical model would be a total shot in the dark. If one could be found it might validate the idea, but with so little to go WRT Titan failing to find one does not kill the idea. I think eliminateing the obvious negatives is the best use for lab tests in that regard at the moment, as you suggest. And Nature always always has surprises in store. the field of cryogenic tholin chemistry in liquid methane/ethane is not exactly mature!

A few other thoughts:

Technically Titans surface has abundant chemical energy - thats where all the material from the upper atmosphere formed by higher energy reactions ends up. What is lacking is many known chemical reactions that can proceed at that temperature to release it.

Titans upper atmosphere is getting more complex every time we look at it - it seems oxygen from other icy moons (http://www.sciencedaily.com/releases/2010/07/100707002535.htm)could get there and form things like amino acids, but the number of possible structures is vast anyway.

The vast number of combinations and low temp could mean Titan has a lot of novel compounds that are only stable at very cold temps, but I'm no chemist...

[transreality]

Look, some one agrees with A.Dim:

yes, it is Chandra Wickramasinghe (http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7451896&fulltextType=RA&fileId=S1473550409990413).

"As we enter a new decade – the year 2010 – a clear pronouncement of our likely alien ancestry and of the existence of extraterrestrial life on a cosmic scale would seem to be overdue."

[baric]

Look, some one agrees with A.Dim:

yes, it is Chandra Wickramasinghe (http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7451896&fulltextType=RA&fileId=S1473550409990413).

"As we enter a new decade – the year 2010 – a clear pronouncement of our likely alien ancestry and of the existence of extraterrestrial life on a cosmic scale would seem to be overdue."

For every crackpot idea, there are a dozen crazies spouting it. But for every solid fact, there are a hundred.

And for every internet forum thread, there's always one guy willing to make up numbers to make a point.

[A.DIM]

Look, some one agrees with A.Dim:

yes, it is Chandra Wickramasinghe (http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7451896&fulltextType=RA&fileId=S1473550409990413).

"As we enter a new decade – the year 2010 – a clear pronouncement of our likely alien ancestry and of the existence of extraterrestrial life on a cosmic scale would seem to be overdue."

How about something more recent from the man?

Viva Panspermia! (http://arxiv.org/ftp/arxiv/papers/1101/1101.4295.pdf)

Working backwards from N=500 at 4 bya to lead to a simple viral-sized genome of say N = 10 (the virus of E coli φX174 has 11 genes), nearly four e-folding times are involved, giving a total evolutionary timescale of nearly 8 billion years, longer than the age of the Earth (cf, Joseph28, Joseph and Schild29).
Hoyle and the present author have dwelt at length on the improbability of obtaining a minimal gene set needed for the emergence of a bacterial genome from random processes. For a set of 500 genes and assuming that 10 sites per gene need to be correctly filled with one of a set of 20 amino acids, the probability turns out to be
~10-6500 . But if only a set of 60 genes can kick start the evolutionary process in the early universe, leading eventually the genes to all life, then the probability is 10-80, which is more easily attainable, and could have been achieved in situations such as have been discussed by Gibson et al27.
Viva panspermia!

:D

[A.DIM]

For every crackpot idea, there are a dozen crazies spouting it. But for every solid fact, there are a hundred.

Indeed, and a solid fact remains that panspermia is more than a crackpot idea, it's a longstanding scientific theory.


And for every internet forum thread, there's always one guy willing to make up numbers to make a point.

Are you suggesting I fabricate numbers to make my points?

[R.A.F.]

Look, some one agrees with A.Dim:

I believe you have that backwards. :)

[baric]

Indeed, and a solid fact remains that panspermia is more than a crackpot idea, it's a longstanding scientific theory.



Are you suggesting I fabricate numbers to make my points?


No, no! Not at all! I was talking about me fabricating the numbers from the previous sentence! :)

My main point was that ideas should stand and fall on their own merits, not based on whom happens to agree or disagree with them.

[Dalkeith]

I think that panspermia is a legitimate area for research.

It does seem to be classified in with the "out there" theories which I consider a bit harsh I did note when I first joined one of the guiding posts specifically highlighted it as a topic of some controversy.

At the end of the day there is life on rocks in space flying about on rocks (the earth) QED its not unreasonable to think there's life on other rocks flying about other bits of space.

[baric]

I think that panspermia is a legitimate area for research.

It does seem to be classified in with the "out there" theories which I consider a bit harsh I did note when I first joined one of the guiding posts specifically highlighted it as a topic of some controversy.

I think it depends on which interpretation of panspermia you are supporting that decides how far "out there" it is.

The idea that complex pre-biotic molecules can form in the cold of space and then "seed" a biological friendly environment like Earth to jump start abiogenesis is not really far out there at all.

This would still result in a separate abiogenesis on each planet and does not imply that biological organisms can survive in space.

[Trakar]

I think it depends on which interpretation of panspermia you are supporting that decides how far "out there" it is.

The idea that complex pre-biotic molecules can form in the cold of space and then "seed" a biological friendly environment like Earth to jump start abiogenesis is not really far out there at all.

This would still result in a separate abiogenesis on each planet and does not imply that biological organisms can survive in space.

More than this, the concept that bacteria might knocked off one planet and survive transit and impact onto another nearby planet, is at least plausible. That such a mechanism might work to spread beyond such nearby neighbors or even across interstellar distances, probably wrings the scientific plausibility out of the concept.

[marsbug]

The idea of lithopanspermia - that rocks expelled into space from Earth during a dinosaur-killer sized impact could reach another planets surface with viable microbes within them - has also been investigated in some depth. The impression I get is that, due to the body of evidence accumulated, lithopanspermia is regarded as being mainstream, plausible, and worth pursueing, if unlikely. The findings of what I read (some time ago) IIRC were that, while the odds of any single microbe making the trip intact were very bad, they were not so bad as to guaruntee wiping out all of a large population of rock dwelling microbes.

The case of a 1 meter rock ejected from the dinosaure impact was the most commonly used. It was found (again IIRC) to be possible that many such rocks could be ejected into space without being heated all the way through, that the time for space radiation to sterilise the entire rock was tens to hundreds of thousands of years (long enough that an interplanetary crossing might realistically occur), and that landing might be survivable, particularly if the rock broke up as it hit the target planets upper atmosphere. It was suggested that the idea was far more plausible early in the Earths history when many impacts that size or bigger took place - more throws of the dice in effect. I'll try to find the papers.

[astromark]

I see something wrong with this idea... Its passing the buck.
By making the suggestion that life came from some place else just avoids the question of how, where, why did it start at all...
Its a cop out., and when you study the detail of bits of rock that 'might' contain life forms being thrown into space by whatever and letting said life spread thus.... really ? It looks a little short of real. Can we be shown proof of this ?

[baric]

I see something wrong with this idea... Its passing the buck.
By making the suggestion that life came from some place else just avoids the question of how, where, why did it start at all...

If you increase the number of environments in which prebiotic molecules can incubate, then you increase the overall chances of abiogenesis as long as you have a mechanism to intermingle between the environments.

"Why", as a question, is a non-sequitur so don't expect an answer for that.

[marsbug]

I see something wrong with this idea... Its passing the buck.
By making the suggestion that life came from some place else just avoids the question of how, where, why did it start at all...


Its only passing the buck if we're lazy: the idea of life originateing elsewhere in the solarsystem (if ever proven) would show us that there is are two questions hidden within 'how did life on Earth start?'. Instead you'd have 'how did life start?' and 'how did it get to Earth?' And if the story is that earth life has travelled elsewhwere it doesn't change a thing.
Anyone claiming that panspermia answeres the question of how life began just hasn't thought about what they're saying. That doesn't stop panspermia being an interesting idea, and if true it could inform our quest to understand how life started by pointing us in the direction of better places to look for clues.

As Baric points out, the 'seeds of life' (as abiogenic carbon chemistry) are much easier to spread than actual life forms.

[astromark]

'Marsbug' understood me. Why didn't 'Baric'. Oh yes.
As a possible answer to how life started on planet Earth I accept this Panspermia as a possible
answer to part of the overall question... but how does it help this conversation ? No, I don't see it either.

[transreality]

Anyone claiming that panspermia answeres the question of how life began just hasn't thought about what they're saying.

"Astronomy continues to reveal the presence of organic molecules and organic dust on a huge cosmic scale, amounting to a third of interstellar carbon tied up in this form. Just as the overwhelming bulk of organics on Earth stored over geological timescales are derived from the degradation of living cells, so it seems likely that interstellar organics in large measure also derive from biology." CW (http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7451896&fulltextType=RA&fileId=S1473550409990413)

Under the doctrines of "Cosmic Ancestry" life precedes or originates with the universe. of course this is just typical of the approach of the panspermist, alot of "seems likely" and "suggests that", and argument by analogy, conjectures built on poor interpretations, and in apparent ignorance of well accepted science. In actual fact, Hydrogen is relatively primordial, Carbon and Oxygen originate in stars, and if they mix in nebula, as is inevitable when stars explode, organic chemistry results, all without requiring 'biology'.

[transreality]

How about something more recent from the man?



I had a look at his Cardiff University page and noticed all of his 2010 publications were in the 'Journal of Astrobiology' (http://journals.cambridge.org/action/displayJournal?jid=IJA), I had a look at a few of the articles in this journal and there is something slightly strange about many of them, I was having a look through the latest to see whether any looked like conventional mainstream science... I'm not sure...I'm pretty sure that the Pivar paper on evolution of the vertebrate skeleton does not correspond to any developmental evolution story i've seen before. Not so sure about the astronomy, and there is alot of panspermia. You should probably check it out.

[Trakar]

If you increase the number of environments in which prebiotic molecules can incubate, then you increase the overall chances of abiogenesis as long as you have a mechanism to intermingle between the environments.

And you can demonstrate that abiogenesis doesn't depend upon a very narrow range, if not precise, set of exacting conditions?

[Swift]

Let's not turn this into yet another panspermia thread. The discussion in this thread on panspermia ends now. If you wish to discuss it, start a new thread or dig up an old one. And if anyone really needs their panspermia post in this thread moved to the new thread, Report your post and it can be moved.

[astromark]

At a interesting 590 post in... have we learned anything ?
With constant and ongoing developments our ability to detect anything is improving.. and, by anything in this context
I am thinking of living things of some technical ability.
Please feel free to update my muddled thoughts on this. As yet we have zero cases to study...

[Colin Robinson]

Returning to the article by AP science writer Seth Borenstein quoted in the OP...


Every new discovery makes it more likely that we are not alone. The case for some kind alien life somewhere else in the universe is steadily building.

The word "likely" may be too strong – clearly there is still plenty of room for different opinions about whether life beyond Earth is likely or not. But there does seem to have been a shift since the 1980s, when Norman Horowitz (a biologist involved in the Viking project) could say:


Since Mars offered by far the most promising habitat for extraterrestrial life in the solar system, it now virtually certain that the earth is the only life-bearing planet in our region of the galaxy. We have awakened from a dream. We are alone… (cited Steven J. Dick; The Biological Universe; Cambridge Universe Press, 1996; p 157)

Back then, observations of Mars and the other planets and moons seemed (to eminent scientists such as Horowitz) to make any sort of life in this solar system extremely unlikely. And back then, the very existence of planets beyond the solar system had not even been established. So the prospects of actually finding even simple forms of life beyond Earth then seemed remote. Unless of course a life-form was going to be kind enough to send us a radio message.

Discoveries in the last 20 years – hundreds of identified exoplanets, plumes of methane on Mars, reassessment of Viking findings about supposed lack of organic compounds in Martian sand, evidence of liquid water inside Enceladus and Europa, the indications of carbon cycling on Titan – these new findings do and should make a difference to how well-informed people think about the question of life beyond Earth.

Seth Borenstein is close to the mark. Life on nearby worlds – I mean, worlds near enough to check out with space probes or at least with space telescopes – increasingly looks, if not likely, at least possible and plausible.

It is, at least, no longer "virtually certain" that there is none.

[Trakar]

Returning to the article by AP science writer Seth Borenstein quoted in the OP...



The word "likely" may be too strong – clearly there is still plenty of room for different opinions about whether life beyond Earth is likely or not. But there does seem to have been a shift since the 1980s, when Norman Horowitz (a biologist involved in the Viking project) could say:

(cited Steven J. Dick; The Biological Universe; Cambridge Universe Press, 1996; p 157)

Back then, observations of Mars and the other planets and moons seemed (to eminent scientists such as Horowitz) to make any sort of life in this solar system extremely unlikely. And back then, the very existence of planets beyond the solar system had not even been established. So the prospects of actually finding even simple forms of life beyond Earth then seemed remote. Unless of course a life-form was going to be kind enough to send us a radio message.

Discoveries in the last 20 years – hundreds of identified exoplanets, plumes of methane on Mars, reassessment of Viking findings about supposed lack of organic compounds in Martian sand, evidence of liquid water inside Enceladus and Europa, the indications of carbon cycling on Titan – these new findings do and should make a difference to how well-informed people think about the question of life beyond Earth.

Seth Borenstein is close to the mark. Life on nearby worlds – I mean, worlds near enough to check out with space probes or at least with space telescopes – increasingly looks, if not likely, at least possible and plausible.

It is, at least, no longer "virtually certain" that there is none.

I see the direction going the other way. The early Grieeks thought that every point of light in the sky was a planet like the earth filled with different forms of life. In the late nineteenth and twentieth centuries Venus was thought to be a rainy, swampy paleo environment and Mars was thought to have vast vegetative bands supported by canali (natural or artificial). Then in late twentieth century (seventies) there were still (imagined) vast bacterial masses on Mars and in cloud top colonies on venus, and every star system with planets was largely identical to ours, with at least 1 terrestrial planet in the habitable zone.

Now, if there is other life in our system it is largely hidden and inaccessible in deep rock mantle zones or under kilometers of ice on gas giant moons. And while we've actually found planets around other stars, they are in systems that generally don't even come close to approximating our system, with planets that our understandings lead us to believe are really not much like anything we are familiar with.

None of this convinces me that we are alone in the universe, but it certainly seems like the likelihood of life as we know and understand it is getting more rare with the passage of time and the increase of our understandings of the universe.

[Colin Robinson]

I see the direction going the other way. The early Grieeks thought that every point of light in the sky was a planet like the earth filled with different forms of life. In the late nineteenth and twentieth centuries Venus was thought to be a rainy, swampy paleo environment and Mars was thought to have vast vegetative bands supported by canali (natural or artificial). Then in late twentieth century (seventies) there were still (imagined) vast bacterial masses on Mars and in cloud top colonies on venus, and every star system with planets was largely identical to ours, with at least 1 terrestrial planet in the habitable zone.

It's true that if you look through past history, you can find arguments in favor of life beyond Earth that seem ridiculous in the light of modern knowledge. You can also, if you look, find arguments against life beyond Earth that are equally laughable in the context of what we know now...

* According to Aristotelian, geocentric cosmology, celestial bodies were made of a different substance than Earth – a lighter, aetherial substance, which is why they didn't fall down from the sky. So, no possibility of embodied life there.
* About 100 years ago, the great biologist Alfred Russel Wallace argued that life would be impossible anywhere in the Milky Way Galaxy except at or near its centre, which was where our Solar System was then supposed to be...
* In the early 20th century, James Jeans put forward the theory of planetary formation being caused by a chance close encounter between two stars, and thought the Solar System might be unique: the one and only instance of a star with planets.



Now, if there is other life in our system it is largely hidden and inaccessible in deep rock mantle zones or under kilometers of ice on gas giant moons. And while we've actually found planets around other stars, they are in systems that generally don't even come close to approximating our system, with planets that our understandings lead us to believe are really not much like anything we are familiar with.

You've drawn attention to the unfamiliar characteristics of other worlds. What I find interesting is the mix of the familiar and unfamiliar. The water fountaining from the surface of Enceladus may come from beneath a thickish layer of ice, but it is still the familiar substance H2O...


None of this convinces me that we are alone in the universe, but it certainly seems like the likelihood of life as we know and understand it is getting more rare with the passage of time and the increase of our understandings of the universe.

I'd agree that life beyond Earth is unlikely to be "life as we know it". Judging by the other stuff we've found beyond Earth, it will be very different in some ways, yet similar in others…

[Trakar]

...I'd agree that life beyond Earth is unlikely to be "life as we know it". Judging by the other stuff we've found beyond Earth, it will be very different in some ways, yet similar in others…

Your supposition of life other than "as we know it" is based upon what evidence?

[HenrikOlsen]

Your supposition of life other than "as we know it" is based upon what evidence?
Life as we know it, in the different habitats here, which shows some of the variability of life, even in as narrow a band as we have available for observation here, would suggest that life elsewhere, if present, will have some properties that are essentially impossible to predict. Even if its circumstances are very similar to here.

I would posit though that one property we would be able to recognize eventually will be reproduction with offspring almost but not entirely identical to the ancestors, and that this will have driven evolution to adapt that life to basically everywhere it could be fitted.

[iquestor]

I think there is almost certainly organic life out there and we will share some basic commonalities with it, like reproduction, resource consumption, metabolism, and evolution. I think there is probably present or past microbial life on mars and elsewhere in the solar system, but probably not higher than say an algae mat; I do not think that the lack of higher life forms in our solar system means that LAWKI is not out there, they just need a planet a little more like Earth. I think that if intelligence is also out there, some of them will have become machine intelligences that may have no similarities to us at all.

[Colin Robinson]

Your supposition of life other than "as we know it" is based upon what evidence?

You sound like a lawyer, defending Mars, Europa and Titan from the charge of harboring undocumented aliens! Well, I can't present proof beyond reasonable doubt, but I would argue there are real and growing grounds for suspicion.

When the findings from Titan were mentioned earlier in this thread, you compared them to depressions in a backyard that someone interpreted as possibly being the footprints of a dragon.

A crucial difference (it seems to me) is the extent to which the territory in question has been studied.

The surface of the Earth has already been explored by naturalists, thoroughly enough to make it most unlikely that there are major new classes of vertebrates which remain to be identified.

It wasn't always that way, though. Two centuries ago, when the first skins and eggs of the platypus were shipped from Australia to Europe, was it in the category of "life as we know it"?

Not to the naturalists of the time, who in fact suspected a hoax. Furry animals did not lay eggs, nor did they have duck-like mouths.

I would compare the Titan findings to apparent footprints of an unknown animal in the mud of a largely unexplored continent, like Australia was (from the European point of view) two hundred years ago.

Yes, it is conceivable they will turn out to be something other than footprints. But if we seriously want to find (or exclude) extraterrestrial organisms, they are the sort of clue we need to follow up.

[Gomar]

Keep in mind that history will record the discovery date, not the verification date.

If *something* is discovered in 2016 and we confirm that it is indeed ET life in 2036, the psi-books of 2100 will most likely record 2016 as the discovery date. So, in that sense, your prediction would be correct. :P

ok, but history books record Columbus finding America in 1492 simply because he could verify it... and did! He had witnesses, artifacts, Indians, etc. that he brought back as proof. And others came after him, so thus he was right.
Ifcourse, the Vikings who landed in America before him did not return as they all died off. Neither was that Chinese admiral given credit for discovering California as he didnt know where he was.

What if, some UFO reports are indeed real, as are some abductions, or writings of visits by angels in the Bible are actually alien contact with humans? Would any of it be considered as 1st proof of alien existence, once ifcourse aliens have been proven to exist? Wouldnt it be funny if aliens do admit to having abducted humans?

[Trakar]

You sound like a lawyer, defending Mars, Europa and Titan from the charge of harboring undocumented aliens! Well, I can't present proof beyond reasonable doubt, but I would argue there are real and growing grounds for suspicion...

I would disagree. The supposition of life "as we imagine it might be" is not "growing grounds" for anything but unfounded speculation or "science fiction" as it is popularly called.

Just because life as we know it seems increasingly hard to sniff out, is no reason to begin presupposing, without the barest hint of empiric support, issues of life "other than as we know it."

[Trakar]

Life as we know it, in the different habitats here, which shows some of the variability of life, even in as narrow a band as we have available for observation here, would suggest that life elsewhere, if present, will have some properties that are essentially impossible to predict. Even if its circumstances are very similar to here.

I would posit though that one property we would be able to recognize eventually will be reproduction with offspring almost but not entirely identical to the ancestors, and that this will have driven evolution to adapt that life to basically everywhere it could be fitted.

If it is carbon nucleotide based life I would consider it life as we know it, if it seems alive and is based on something else, then I would say it has a good chance to be life not as we know it. I've seen no evidence of life as we don't know it, virii and some basic protein structures (prions) come close, but look to be degradations and mutations of more traditional carbon nucleotide life. I'm uninterested in what form or habitat life as we know it adapts to fit, it is still life as we know it. so far the only type of life we can confirm and compellingly support as existing is life as we know it. So far, the only examples of life as we know it, come from our own planet. As far as we can tell, all of the life on our planet is not just the same type of life, it is all apparently related. Not just the same "kind" of life, the same "life," common ancestry.

[Colin Robinson]

I would disagree. The supposition of life "as we imagine it might be" is not "growing grounds" for anything but unfounded speculation or "science fiction" as it is popularly called.

Just because life as we know it seems increasingly hard to sniff out, is no reason to begin presupposing, without the barest hint of empiric support, issues of life "other than as we know it."

A quotation from the 2008 NASA Astrobiology Roadmap (downloadable from http://astrobiology.nasa.gov/roadmap) (page 718)


The existence of lakes of liquid hydrocarbons on Titan opens up the possibility for solvents and energy sources that are alternatives to those in our biosphere and that might support novel life forms altogether different from those on Earth.

Is this an instance of what you call "unfounded speculation", "science fiction" etc, Trakar?

[Paul Beardsley]

Is this an instance of what you call "unfounded speculation", "science fiction" etc, Trakar?

Saying "might support novel life forms altogether different from those on Earth" is founded speculation. It's a cautiously general expression of something that is conceivably possible but clearly unknown.

Saying "life on Titan will take the form of crabs with three claws" would be unfounded speculation.

[iquestor]

Saying "might support novel life forms altogether different from those on Earth" is founded speculation. It's a cautiously general expression of something that is conceivably possible but clearly unknown.

Saying "life on Titan will take the form of crabs with three claws" would be unfounded speculation.

Thats ridiculous. Titan Crabs have 5 claws.

[Trakar]

A quotation from the 2008 NASA Astrobiology Roadmap (downloadable from http://astrobiology.nasa.gov/roadmap) (page 718)



Is this an instance of what you call "unfounded speculation", "science fiction" etc, Trakar?

That is simple speculation based largely on the potential of finding life as we do know it. What I am calling "science fiction" is the supposition that places unfit to produce and sustain life as we know it, will generate and sustain life as we don't know it and that such speculated life as we don't know it is a viable alternative without a single example or instance of life as we don't know it to point to as evidence that life as we don't know it is even possible.

[Colin Robinson]

Saying "might support novel life forms altogether different from those on Earth" is founded speculation. It's a cautiously general expression of something that is conceivably possible but clearly unknown.

Saying "life on Titan will take the form of crabs with three claws" would be unfounded speculation.

Yes, "founded speculation" is a good term. Another term might be "conjecture", as in Karl Popper's view that science advances through "conjectures and refutations".

The conjecture, or speculation, that Titan is a world with "novel life forms" may eventually get refuted. But it is at least founded on known principles of chemistry and thermodynamics, and on what is now known about conditions on Titan itself.

Indeed, Chris McKay's prediction that the proliferation of life on Titan would be likely to have measurable effects on atmospheric composition – less H2 and less acetylene near the surface than otherwise expected – this argument might well have led to a sort of refutation. Instead the conjecture has survived, with enhanced credibility.

Popper compared science to a search-light... It is very true, as Trakar keeps reminding us, that not a single example of life beyond earth has yet been discovered. But perhaps that is simply because a bright enough search-light has not so far been directed at places such as Titan where founded speculation says life may exist?

[Trakar]

...But perhaps that is simply because a bright enough search-light has not so far been directed at places such as Titan where founded speculation says life may exist?


er,..."...where founded speculation *suggests some form of life as we understand it* may exist."

:razz:

[R.A.F.]

Saying "might support novel life forms altogether different from those on Earth" is founded speculation. It's a cautiously general expression of something that is conceivably possible but clearly unknown.

So disagreeing with that would be unfounded speculation?

No...I don't think so...not unless you can demonstrate that life actually exists elsewhere...not speculate, demonstrate.

[Paul Wally]

So disagreeing with that would be unfounded speculation?

No...I don't think so...not unless you can demonstrate that life actually exists elsewhere...not speculate, demonstrate.

But how do you demonstrate something if you don't first speculate that it might possibly exist wherever you intend to look for it. If your approach is followed we will have to send a probe to every nook and cranny of the solar system simply because we dislike hypothetical thinking. Hypothesis (or speculation as you like to call it) precedes demonstration. That's standard scientific method.

[Daffy]

But how do you demonstrate something if you don't first speculate that it might possibly exist wherever you intend to look for it. If your approach is followed we will have to send a probe to every nook and cranny of the solar system simply because we dislike hypothetical thinking. Hypothesis (or speculation as you like to call it) precedes demonstration. That's standard scientific method.

Well said!

[R.A.F.]

Hypothesis (or speculation as you like to call it) precedes demonstration.

Hypothesis are based on evidence, while speculation need not be...2 different things.


If your approach is followed we will have to send a probe to every nook and cranny...

Unless you can show just where I said anything like that, please don't put words into my mouth that I did not say.

[Paul Beardsley]

Unless you can show just where I said anything like that, please don't put words into my mouth that I did not say.

It's how Post 607 looked to me. At least that was the best interpretation I was able to come up with.

[R.A.F.]

It's how Post 607 looked to me. At least that was the best interpretation I was able to come up with.

Well, that just shows that we can both be wrong. :)

[eburacum45]

What I am calling "science fiction" is the supposition that places unfit to produce and sustain life as we know it, will generate and sustain life as we don't know it and that such speculated life as we don't know it is a viable alternative without a single example or instance of life as we don't know it to point to as evidence that life as we don't know it is even possible.The history of the Earth is full of life as we don't know it. For almost all its history, our planet was significantly different to how it is today; for much of that time, there was little or no free oxygen. Carbon dioxide and even oxygen levels have fluctuated considerably, and even the luminosity of the Sun has changed over time.

Life has changed considerably, even since the advent of multicellular organisms. The Ediacara biota is a particular example.
http://en.wikipedia.org/wiki/Ediacara_biota
We know that life as we don't know it existed on Earth, long ago; we can be certain that, if life exists elsewhere, it will not be as we know it.

[Colin Robinson]

Unless you can show just where I said anything like that, please don't put words into my mouth that I did not say.

So how, in your view, can the question of life elsewhere in the solar system be resolved?

(a) By short listing the planets and moons which are plausible habitats, and investigating those places with space probes?
(b) By looking everywhere in the solar system?
(c) By considering it a non-question until and unless conclusive evidence arrives serendipidously on Earth (i.e. living organisms in a meteorite)?
(d) Or...?

[Trakar]

But how do you demonstrate something if you don't first speculate that it might possibly exist wherever you intend to look for it. If your approach is followed we will have to send a probe to every nook and cranny of the solar system simply because we dislike hypothetical thinking. Hypothesis (or speculation as you like to call it) precedes demonstration. That's standard scientific method.

You send probes where there is the most likelihood of there being conditions you believe conducive to the formation of life, as you understand that process,...so far, either our understanding is much further off than is popularly believed, or life is a much rarer proposition than is commonly considered.

Nothing wrong with speculation, so long as it is properly qualified and understood as such. The problems come when these speculations turn into beliefs and convictions that aren't supported by available evidences.

((Oh, and just to stay true to actual definitions

hy·poth·e·sis Noun /hīˈpäTHəsis/
1. A supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.

http://www.google.com/search?q=define+hypothesis&hl=en&num=10&lr=&ft=i&cr=&safe=images&tbs=#hl=en&lr=&q=hypothesis&tbs=dfn:1&tbo=u&sa=X&ei=tMmLTujeFMevsQLW85GrBA&ved=0CCUQkQ4&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=e0d9278042d8f40f&biw=1024&bih=645))

[Trakar]

The history of the Earth is full of life as we don't know it. For almost all its history, our planet was significantly different to how it is today; for much of that time, there was little or no free oxygen. Carbon dioxide and even oxygen levels have fluctuated considerably, and even the luminosity of the Sun has changed over time.

Neither I, nor any biologist I am familiar with, would consider any of these variations to be "life as we don't know it." All life we are familiar with is based on the same carbon root amino acids, and came from the same progenitor ancestral life strain,...to the best of our ability to determine. Why should we consider any such life to be "life as we don't know it?"



Life has changed considerably, even since the advent of multicellular organisms. The Ediacara biota is a particular example.

And what about the Ediacara biota leads you to conclude that they are fundementally and substantively brothers from a seperate mother? As far as I can tell they are believed to be an extinct line but nonetheless still of the common Terrestrial tree of life.



We know that life as we don't know it existed on Earth, long ago; we can be certain that, if life exists elsewhere, it will not be as we know it.

If you have evidence indicating that the Ediacara are anything other than another (failed) branch of Terrestrial life,...please present it.

[Trakar]

So how, in your view, can the question of life elsewhere in the solar system be resolved?...

My personal resolution of the issue: until compelling evidence of the existence of such life is found, I simply don't presume its existence.

[eburacum45]

If you have evidence indicating that the Ediacara are anything other than another (failed) branch of Terrestrial life,...please present it.The Ediacara were almost certainly descended from the same ancestral microbiota that all other life on Earth is descended from. (There is a small possibility that they were, in fact completely unrelated, but we will probably never know, since no genetic evidence survives).


But they were most definitely life as we don't know it; nothing about that biota resembles life on Earth today- they don't even seem to have proper bilateral symmetry; instead they have 'glide symmetry', where features are repeated on each side of the line of symmetry but are displaced. There is nothing about the Ediacarans which could be predicted by examining life on Earth as we see it today; that makes it 'life as we do not know it' in my book.

If there is any aspect of the Ediacaran biota which you can confidently state conforms with 'Life as we know it' please present it; this could be an instructive exercise, as any such feature you present may in fact be a universal feature, which is likely to be repeated in any multicellular biota throughout the universe.

[astromark]

Post 619 and we still can not confirm that some life form has been found off planet Earth.. Not one.

Not evidence of it.. or even a environment that can support life as we know it.. not one...

and as unacceptable as that is. Its for the moment all we have.. NOTHING.

So I come down on this with a view distasteful, but true..

The preposition that 'Evidence for ET is mounting' Is not supported by science..

[Jeff Root]

I composed something years ago for a web page, giving my
opinion of what is meant by the expression "life as we know it".
I only counted that it is based on carbon, depends on water, and
is organized into cells. But that's just my opinion.

The page is still unfinished: http://www.freemars.org/jeff/answers/

-- Jeff, in Minneapolis

[Strange]

So disagreeing with that would be unfounded speculation?

That is a false dilemma: speculating that life may exist or may not exist are both well founded.

[Moose]

My personal resolution of the issue: until compelling evidence of the existence of such life is found, I simply don't presume its existence.

What Trakar said. One can speculate, one can be cautiously optimistic, one can make educated guesses, one can hypothesize, one can search according to priorities, one can even make it one's life's work. All of that is valid. But belief and conclusion are premature. There is no evidence, at all, upon which to hang those hats.

[R.A.F.]

What Trakar and Moose said. :)

[Colin Robinson]

hy·poth·e·sis Noun /hīˈpäTHəsis/
1. A supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.

http://www.google.com/search?q=define+hypothesis&hl=en&num=10&lr=&ft=i&cr=&safe=images&tbs=#hl=en&lr=&q=hypothesis&tbs=dfn:1&tbo=u&sa=X&ei=tMmLTujeFMevsQLW85GrBA&ved=0CCUQkQ4&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=e0d9278042d8f40f&biw=1024&bih=645))

If a hypothesis is made on the basis of evidence, but a hypothesis is still something different from an established fact, then it logically follows that evidence is not necessarily the same thing as proof.


Post 619 and we still can not confirm that some life form has been found off planet Earth.. Not one...
The preposition that 'Evidence for ET is mounting' Is not supported by science..

If you take "evidence" to mean the same thing as "proof", then the proposition that "evidence is mounting, but not proven" would the same as saying "proof is increasing, but there is still no proof" – self-contradictory.

If you take "evidence" to mean "data consistent with a hypothesis", it is another matter. For instance, plumes of methane detected in the atmosphere of Mars are data consistent with the hypothesis than there are methane-producing organisms there.

[Trakar]

The Ediacara were almost certainly descended from the same ancestral microbiota that all other life on Earth is descended from. (There is a small possibility that they were, in fact completely unrelated, but we will probably never know, since no genetic evidence survives).


But they were most definitely life as we don't know it; nothing about that biota resembles life on Earth today- they don't even seem to have proper bilateral symmetry; instead they have 'glide symmetry', where features are repeated on each side of the line of symmetry but are displaced. There is nothing about the Ediacarans which could be predicted by examining life on Earth as we see it today; that makes it 'life as we do not know it' in my book.

If there is any aspect of the Ediacaran biota which you can confidently state conforms with 'Life as we know it' please present it; this could be an instructive exercise, as any such feature you present may in fact be a universal feature, which is likely to be repeated in any multicellular biota throughout the universe.

I would not consider any of the above as distinctions seperating Ediacaran from "life as we don't know it." So long as it is based on the same RNA/DNA protein chemistries as the rest of earth life, the forms and expressions of that life are irrelevent to my considerations of "as we know it" or not. Personally, I'd be very open to accepting any carbon-chemistry based life as "life as we know it." At least there is a basis for supporting that "other carbon chemistry life" may well exist, no evidence of it, but by simple extension of the chemistries we already (kinda-sorta) understand, it would be a reasonable consideration. And given this, we know of one specific type of environment that can yeild carbon life. Likewise, we know that even relatively small variations from that specific environment seem unable to produce, or at the least, sustain, carbon life (at least in abundances sufficient to make it obvious).

[eburacum45]

Since we don't actually know for sure that the Ediacara biota had the same biochemistry as ourselves,we should really only consider the morphology. The morphology was unlike anything we are familiar with.

Similarly we should expect any extraterrestrial life to be unlike anything we are familiar with. The fossil record shows that there is a very large range of possible lifeforms and a very large range of possible environments which can support life. So far we have only encountered a tiny fraction of those possible lifeforms and possible environments.

[transreality]

Not really... the symmetry of the ediacaran is the same degree of symmetry as just about any leaf you may look at. They don't have the strict bilateral symmetry of alot of animalia, but then they are most likely to be some sort of organism derived from algae.

[R.A.F.]

If you take "evidence" to mean "data consistent with a hypothesis", it is another matter. For instance, plumes of methane detected in the atmosphere of Mars are data consistent with the hypothesis than there are methane-producing organisms there.

Are there no other explanations for the presence of methane on Mars?

[Paul Wally]

Are there no other explanations for the presence of methane on Mars?

Occam's Razor is not a judge of truth. Even if there is a geological explanation, just the possibility that the methane plumes could possibly be of biological origin makes it a worthy hypothesis to follow up on. If we are trying to find life then we should follow up on the clues that could possibly lead us there. And if it turns out that the plumes are of geological origin then so be it. But not pursuing a line of investigation simply because there is a simpler boring explanation, that may possibly be false, doesn't make much sense to me.

[John Jaksich]

Occam's Razor is not a judge of truth. Even if there is a geological explanation, just the possibility that the methane plumes could possibly be of biological origin makes it a worthy hypothesis to follow up on. If we are trying to find life then we should follow up on the clues that could possibly lead us there. And if it turns out that the plumes are of geological origin then so be it. But not pursuing a line of investigation simply because there is a simpler boring explanation, that may possibly be false, doesn't make much sense to me.



I have often felt that way, also---but when I have looked closer at my lines of reasoning--I have come to realize that there are occasions when one tends to let "emotional" reasoning sway there better judgement. Don't get me completely wrong---there is truth to your statement but a simple explanation entails that the further investigation the phenomenon could involve complexities of which you are currently inferring and possibly (?) hoping to be true.

My personal advice is to not give up but don't completely give into your emotions.

I truly hope that I was able to reach you.

John

[R.A.F.]

Occam's Razor is not a judge of truth. Even if there is a geological explanation, just the possibility that the methane plumes could possibly be of biological origin makes it a worthy hypothesis to follow up on. If we are trying to find life then we should follow up on the clues that could possibly lead us there. And if it turns out that the plumes are of geological origin then so be it. But not pursuing a line of investigation simply because there is a simpler boring explanation, that may possibly be false, doesn't make much sense to me.

I'm curious as to Colin's answer, but thanks for the simple yes or no response. :)

[iquestor]

Methane on Mars - my understanding is that, in humanity's experience, methane is produced either by volcanoes, or a by product of life. Its half life is only about 300 years so that the presence of it in mars atmosphere is intriguing, especially taken with the evidence for water, both past and present, however Mars has been a very volcanically active planet and possibly is today.

could it be volcanism creating the methane plumes on Mars? sure. but it could also be life. there are plenty of other indicators of the potential for life there to go and find out!

[Trakar]

Since we don't actually know for sure that the Ediacara biota had the same biochemistry as ourselves,we should really only consider the morphology. The morphology was unlike anything we are familiar with.

Similarly we should expect any extraterrestrial life to be unlike anything we are familiar with. The fossil record shows that there is a very large range of possible lifeforms and a very large range of possible environments which can support life. So far we have only encountered a tiny fraction of those possible lifeforms and possible environments.

Big difference between the range of conditions life can adapt to given time and exploitable energy to take advantage of, and the range of conditions suitable for the formation of life. Finding life in a large range of habitats says very little about where we might expect life to form, and that is much more important than conditions which we may think or can demonstrate that life can adapt to.

[transreality]

Ancient methane could also be released from methane clathrate (http://en.wikipedia.org/wiki/Methane_clathrate) ices that are sublimating after being exposed by erosion. The same reason methane is detected in comets.

[Colin Robinson]

Are there no other explanations for the presence of methane on Mars?

There are other possible explanations, yes – other hypotheses consistent with the data.

What Paul Wally said, is how I see it also...


...just the possibility that the methane plumes could possibly be of biological origin makes it a worthy hypothesis to follow up on. If we are trying to find life then we should follow up on the clues that could possibly lead us there. And if it turns out that the plumes are of geological origin then so be it.

In any case, the presence of methane in Mars' atmosphere requires some explanation, because it is an anomaly, in the sense that methane can't just hang about indefinitely in the sort of atmosphere Mars has.

A possibly relevant quote from the biologist Lynn Margulis (one of the originators of the Gaia Hypothesis) back before the methane was found. She was being interviewed by Stewart Brand of the CoEvolution Quarterly, and she explained why she thought there was no life on Mars:


Margulis:You see, there are no reduced compounds in the presence of the oxidized ones. Which is our clue. Everything's essentially oxidized.
SB: If there were life you'd look for what gases?
Margulis:You'd look for ammonia, methane, hydrogen, or hydrogen sulfide or any of these things that are flagrant contradictions in the presence of oxygen and CO2...

Source: Steward Brand (ed); Space Colonies; Penguin 1977; page 124.

[Colin Robinson]

I have often felt that way, also---but when I have looked closer at my lines of reasoning--I have come to realize that there are occasions when one tends to let "emotional" reasoning sway there better judgement. Don't get me completely wrong---there is truth to your statement but a simple explanation entails that the further investigation the phenomenon could involve complexities of which you are currently inferring and possibly (?) hoping to be true.

My personal advice is to not give up but don't completely give into your emotions.

Do you think that emotion wants life beyond Earth to exist, while reason is on the other side?

I would question that.

About 100 years, Alfred Russel Wallace (one of the pioneers of the theory of evolution) wrote a book called Man's Place in the Universe, where he said that the idea of many inhabited worlds "would imply that man is... of no importance".

Conversely, if Earth is the only world with life, and we humans are the dominant life form on it, that makes the human race a big frog in a small pond.

Maybe this is why many humans are reluctant to take seriously the idea of life beyond Earth?

[John Jaksich]

Do you think that emotion wants life beyond Earth to exist, while reason is on the other side?

I would question that.

About 100 years, Alfred Russel Wallace (one of the pioneers of the theory of evolution) wrote a book called Man's Place in the Universe, where he said that the idea of many inhabited worlds "would imply that man is... of no importance".

Conversely, if Earth is the only world with life, and we humans are the dominant life form on it, that makes the human race a big frog in a small pond.

Maybe this is why many humans are reluctant to take seriously the idea of life beyond Earth?


Emotions are what they are---electrochemical impulses from certain parts of the brain to whatever response that may be eliciting them--and for the most part (from what I understand) impulsive.

Individuals for the most part (IMO) may come in two (?) flavors: those who will do the fight/flight response (since our ancestors had to learn to fend for themselves from large predators). . . . and those who have learned to become more cerebral (and thus mindful of their surroundings) . . . thus think before acting on impulse (as cited above).

Because of that notion (cited above) those individuals may not completely understand the implications of their own place in the cosmos.

In regards to A. R. Wallace's work --I had heard of him but have yet to read his work and do know that he was a contemporary of Darwin's. His opinion, conclusions and data cited in his book are probably (?) far-reaching and (?) correct . . .


My observations of humanity (although I am not a behavioral biologist--nor psychologist) tell me that we (humanity) as a species will still evolve as long as we do not wipe ourselves off the planet . . . and the reason for many individuals ambivalence for ET or ETI is because we (?) are much too wrapped up with our own lives (and believe we are the center of the Universe . . . still).

We are currently hard-wired to respond emotionally. . . first . . . and if a wiser head prevails . . . stop, think, weigh the options (?) and respond.

Those more enlightened few do this everyday and probably on the drop of dime (if you can pardon the expression?).

All the best

John

[Paul Beardsley]

Regarding the emotional aspect, I think a lot of people share my stance: I really, really want there to be life out there, and I really want to know for certain that there is life out there. However, above all else I want the truth, even if it isn't the truth I hoped for. I don't want to pretend that something is evidence when it is not. I will not grasp at straws!

I actually feel hatred for the sort of UFO proponent who deliberately mischaracterises skeptics such as myself as being closed-minded and opposed to the idea of there being life. We are not in denial; when real evidence is found, it will be impossible to deny.

[eburacum45]

...the symmetry of the ediacaran is the same degree of symmetry as just about any leaf you may look at. They don't have the strict bilateral symmetry of alot of animalia, but then they are most likely to be some sort of organism derived from algae.
Quite. I've seen this sort of symmetry a lot in botanical contexts. Perhaps if these creatures developed into mobile animal-like forms we might have seen animals that look like plants, and vice versa.
Here's an image I've made of an imaginary 'animal' that shows plant-like characteristics, including an alternating morphological pattern
http://www.orionsarm.com/im_store/leafant.JPG
there aren't any extant animals I can think of with this sort of morphology, but they may emerge on other worlds.

[Colin Robinson]

In regards to A. R. Wallace's work --I had heard of him but have yet to read his work and do know that he was a contemporary of Darwin's. His opinion, conclusions and data cited in his book are probably (?) far-reaching and (?) correct . . .

Wallace was undoubtedly a great scientist, one of the pioneers of modern biology.

Regarding his book Man's Place in the Universe, some of the ideas in it are still widely accepted (though not beyond all debate), e.g. the idea that the Solar System has a "temperate zone", basically meaning the same as "habitable zone" or "Goldilocks zone".

On the other hand, Wallace argued (or should I say speculated) that life may not be possible in the Milky Way Galaxy anywhere except at or near its center.

At the time, many good astronomers thought that's where our Solar System was. And Wallace thought it unlikely to be a coincidence that the only known inhabited world was in such a special cosmic location…

[R.A.F.]

There are other possible explanations, yes – other hypotheses consistent with the data.

What Paul Wally said, is how I see it also...

So you made a conscious, subjective decision as to which explanation you will accept?


How is that not "cherry picking" the data??

[Paul Beardsley]

So you made a conscious, subjective decision as to which explanation you will accept?


How is that not "cherry picking" the data??

Colin Robinson and Paul Wally talked about following up possibilities, not choosing beliefs.

[R.A.F.]

Colin Robinson and Paul Wally talked about following up possibilities, not choosing beliefs.

Yet that is exactly what they did...is there any mention of a geologic explanation before I forced the issue??

Nope...cherry picking, plain and simple.

[Strange]

Are there no other explanations for the presence of methane on Mars?

Of course there are. That is what "consistent with" means; it is one possible explanation.

[Paul Wally]

So you made a conscious, subjective decision as to which explanation you will accept?


How is that not "cherry picking" the data??

Nobody is accepting anything. The hypothesis will only be accepted as true when conclusive evidence is found, e.g. if microbes are found. In the mean time
there is no acceptance, presumption, belief etc. I think, this has been the problem all along; hypothesis is being equated with belief.

[R.A.F.]

My error for not making myself clear. 1st off, I knew the answer to the question before I asked it. I wanted to see what reaction It would illicit. I was not disappointed.

2nd, when you have 2 completely different explanations for the same phenomena, it isn't very forthcoming to not mention both when discussing the phenomena.

3rd, there was no mention of a geological explanation until I "asked" if there were any other explanations besides life that would explanation the phenomena.


..and with that, I'm out of this thread...it ain't worth arguing about.

[Trakar]

Of course there are. That is what "consistent with" means; it is one possible explanation.

Can you link or reference a respectable source that supports this interpretation of "consistent with?"
(or at the least clarify this statement so that it is "consistent with" standard understandings. - to my reading, "consistent with" states or implies nothing about alternate possibities or potentialities.)

[Trakar]

Nobody is accepting anything. The hypothesis will only be accepted as true when conclusive evidence is found, e.g. if microbes are found. In the mean time
there is no acceptance, presumption, belief etc. I think, this has been the problem all along; hypothesis is being equated with belief.

Properly qualified remarks are rarely misunderstood or misinterpreted.

[Paul Wally]

Can you link or reference a respectable source that supports this interpretation of "consistent with?"
(or at the least clarify this statement so that it is "consistent with" standard understandings. - to my reading, "consistent with" states or implies nothing about alternate possibilities or potentialities.)

I think it is quite clear in this context what "consistent with" means. It means that the available evidence does not contradict the hypothesis. It doesn't then require a great conceptual leap to understand that a limited set of evidence can be consistent with a number of different, even conflicting, hypotheses. Ever, heard of a crucial experiment? It is an experiment exactly designed to decide between different explanations of the same data. The case of the methane plumes (data) requires something like a crucial experiment that would decide between different explanations. I think at the moment it is safe to say that we don't know whether the methane is produced by living organisms or some other means, and this will require further observations that will decide between the different hypotheses.

[Paul Wally]

Properly qualified remarks are rarely misunderstood or misinterpreted.

I strongly suspect that this is one of those rare cases.

[Colin Robinson]

Regarding the emotional aspect, I think a lot of people share my stance: I really, really want there to be life out there, and I really want to know for certain that there is life out there. However, above all else I want the truth, even if it isn't the truth I hoped for. I don't want to pretend that something is evidence when it is not. I will not grasp at straws!

I actually feel hatred for the sort of UFO proponent who deliberately mischaracterises skeptics such as myself as being closed-minded and opposed to the idea of there being life. We are not in denial; when real evidence is found, it will be impossible to deny.

I'd agree that if there is extraterrestrial life close enough to detect, and if the effort is made to find it, it will one day be as undeniable as the presence of lichen in Antarctica.

I'd suggest, though, that its discovery may involve several steps, like the discovery of the element helium in the 19th century -- first a bright yellow line in the solar spectrum, which some thought indicated a new element, but was hardly undeniable proof of one; then a few years later someone found the same bright line in a lava spectrum on Earth; and then finally the undeniable stage, when helium was successfully isolated in a laboratory...

[Strange]

Can you link or reference a respectable source that supports this interpretation of "consistent with?"
(or at the least clarify this statement so that it is "consistent with" standard understandings. - to my reading, "consistent with" states or implies nothing about alternate possibities or potentialities.)

You are right. I probably rather overstated the case. (I was going to write something much longer but it was getting late).

I was intending to contrast "consistent with" and a word like "confirms" (for example). If someone said that something (e.g. methane) "confirmed" the existence of life then they would be effectively ruling out other explanations (and, one would hope, relying on a lot of other evidence beside that). Saying that it is "consistent with" life says nothing about other possible explanations; it doesn't rule them out and doesn't guarantee there are others. But it certainly allows others.

I don't see why someone discussing one possibility has to, every time, list every other possibility as well. Especially in an informal context and especially when they are using cautious language such as "consistent with", "may" and "possible". I was just (over?) reacting to the way such statements are often met with "prove it" or "what about X as a possibility". I agree such a response is appropriate if someone were to say "there is life on planet xxx" but not just because they are discussing possibilities.

[Strange]

Do you think that emotion wants life beyond Earth to exist, while reason is on the other side?

I think it depends on the individual (and, perhaps their cultural background and values).


About 100 years, Alfred Russel Wallace (one of the pioneers of the theory of evolution) wrote a book called Man's Place in the Universe, where he said that the idea of many inhabited worlds "would imply that man is... of no importance".

I don't understand that idea at all. My feeling about the discovery of any sort of life (simple or intelligent) elsewhere, is one of great excitement about the new areas of understanding it would open up. I don't see how it would change us; we would still be exactly who we are now.


Conversely, if Earth is the only world with life, and we humans are the dominant life form on it, that makes the human race a big frog in a small pond.

I don't know. Doesn't leave us exactly the same but in a much, much bigger pond?


Maybe this is why many humans are reluctant to take seriously the idea of life beyond Earth?

It may account for some. Who knows whether it is a few, many, or most.

[Swift]

<snip>
My error for not making myself clear. 1st off, I knew the answer to the question before I asked it. I wanted to see what reaction It would illicit. I was not disappointed.

R.A.F.

Chill with the attitude. People are having a friendly discussion about possibilities and speculations. No one seems to be advocating any particular non-mainstream ideas. Don't 'test' people as to whether they are matching some expectation you have of their behavior. If you want to participate in the discussion, then actually participate. If that's not to your liking, then maybe you should stay out of thread.

[Moose]

I just want to add this, then I think I'm more or less done with this topic again.

Observation: Methane on Mars...
a) Hypothesis: ...indicates life.
b) Hypothesis: ...indicates volcanic activity.
c) Hypothesis: ...indicates "recently" exposed methane ice.
d) Hypothesis: ...indicates some other phenomenon we haven't observed yet.

While the highly improbable but highly desirable Hypothesis A would be the ultimate in discoveries, it in no way diminishes the importance and "Wanna know right now; when does the probe get there? Get it there faster, NASA!" factor of all three other possibilities.

Just sayin'.

[Moose]

Actually, I take that back, slightly. I do have one more thing to say for the moment.


I don't understand that idea at all. My feeling about the discovery of any sort of life (simple or intelligent) elsewhere, is one of great excitement about the new areas of understanding it would open up. I don't see how it would change us; we would still be exactly who we are now.

I do. See how it would change us, I mean.

Think back... The (widespread) knowledge that the sky isn't an overturned bowl changed us forever. The repeated discoveries that we're not really the center of anything in time and space, except our own ignorance, helped bring about radical and progressive changes in how we think about ourselves and how we interact with the world. Changes that were invariably met with a great deal of kicking, screaming, upheaval and death (both real and threatened). A very large fraction of the world's population is wailing incessantly over the notion that we've distant common ancestry with every other critter on the planet. We're still choking on the notion that we've common ancestry with ourselves.

If scientific discoveries have not changed us, why all the fuss?

No, our science is dragging us into the future by the scruffs of our necks, sweeping along the unwilling with each next discovery that reveal how we're a much smaller player in a much _much_ larger universe than we've ever imagined possible. This is necessary, if uncomfortable and humbling, and ultimately the very best thing for us.

... I just think it's important to let the science educate us in its time, and not anticipate its revelations.

[Trakar]

You are right. I probably rather overstated the case. (I was going to write something much longer but it was getting late).

I was intending to contrast "consistent with" and a word like "confirms" (for example). If someone said that something (e.g. methane) "confirmed" the existence of life then they would be effectively ruling out other explanations (and, one would hope, relying on a lot of other evidence beside that). Saying that it is "consistent with" life says nothing about other possible explanations; it doesn't rule them out and doesn't guarantee there are others. But it certainly allows others.

I don't see why someone discussing one possibility has to, every time, list every other possibility as well. Especially in an informal context and especially when they are using cautious language such as "consistent with", "may" and "possible". I was just (over?) reacting to the way such statements are often met with "prove it" or "what about X as a possibility". I agree such a response is appropriate if someone were to say "there is life on planet xxx" but not just because they are discussing possibilities.

Try replacing the term "consistent with" with the synonomous terms "agrees with" or "is supporting of" and you will probably more easily see why there is some "bristling" among those who require compelling evidences before they engage their "belief" engines.

http://dictionary.reference.com/browse/consistent

http://www.thefreedictionary.com/consistent

http://www.merriam-webster.com/dictionary/consistent

[Strange]

Try replacing the term "consistent with" with the synonomous terms "agrees with" or "is supporting of" and you will probably more easily see why there is some "bristling" among those who require compelling evidences before they engage their "belief" engines.

OK. I accept that different people will use words and interpret them differently (from me and from each other). And that this could cause problems.

(I am slightly surprised that, in a scientific discussion, anyone would use it to mean anything but "not contradictory". In other words, that anyone would use it differently from me. :) But, hey ho.)

[Paul Beardsley]

Try replacing the term "consistent with" with the synonomous terms "agrees with" or "is supporting of" and you will probably more easily see why there is some "bristling" among those who require compelling evidences before they engage their "belief" engines.

The core meaning is clear. When used in a scientific discussion, especially a speculative one, it is understood to mean "does not disagree with" rather than actively agrees. I don't think there's any excuse for "bristling".

[Paul Wally]

Try replacing the term "consistent with" with the synonomous terms "agrees with" or "is supporting of" and you will probably more easily see why there is some "bristling" among those who require compelling evidences before they engage their "belief" engines.



The issue is that the same evidence can be explained by different theories. So it is conceivable that some observations can be consistent with, agree with or be supporting of different theoretical explanations. Replacing "consistent with" with these synonyms doesn't make any appreciable difference, as far as I can see. I think what you have a problem with is the underdetermination of theory by evidence (http://plato.stanford.edu/entries/scientific-underdetermination/).

[Trakar]

The core meaning is clear. When used in a scientific discussion, especially a speculative one, it is understood to mean "does not disagree with" rather than actively agrees. I don't think there's any excuse for "bristling".

I'd disagree with what you determine to be "clear," especially when the users of the language seem to be insisting on casual understandings and interpretations rather than employing stricter, and more proper scientific qualifications, only begrudgingly acknowledge the range of actual science evidences when dragged to them, and then use such casually misstated arguments in the support of assertions that are quite simply unsupported by the evidences (eg "Evidence for ET is mounting daily"). The word doesn't cause "bristling," the repeated and continuing context of its misusage and misapplication can, however, have that effect on some people.

[Jeff Root]

The meaning of the term "consistent with" in general seems very clear,
and I haven't noticed it being misused in this thread. The surprising thing
is that its use here has been criticized.

While the title of the thread could have been better worded, its meaning
is clear, too, and the reason for the second clause is perfectly clear.
I agree with the title, as I said back in post # one-hundred-something.
There is more and more evidence, perhaps not mounting literally every
day, but frequently, which supports the idea that ETs can be out there.
That is evidence *for* ETs. On the other hand, as far as I know,
we don't yet have any evidence *of* ETs, which is what the second
clause states, as a warning not to misinterpret the first clause.

-- Jeff, in Minneapolis

.

[Paul Beardsley]

What Jeff said.

[Paul Wally]

I don't see what the big deal is here anyway. If the current evidence is not conclusive, then that means that we cannot yet conclude that we have evidence of ET.
In any case, if such conclusive evidence is eventually found, does the process by which we arrived at that evidence really matter? I think not. It doesn't matter whether we take a random guess, theorize, speculate (unfounded or founded) or flip a coin in order to discover conclusive evidence of ET. So what is needed in order to discover ET is a powerful heuristic, and this does not necessarily include having a correct theory of ET beforehand.

[eburacum45]

Big difference between the range of conditions life can adapt to given time and exploitable energy to take advantage of, and the range of conditions suitable for the formation of life. Finding life in a large range of habitats says very little about where we might expect life to form, and that is much more important than conditions which we may think or can demonstrate that life can adapt to.

Also true, but we can't be certain what conditions were suitable for the formation of life, so we can't say much about the locations where it might be expected to emerge. Although we may assume with some confidence that abiogenesis occured on this planet at some point in the distant past, there are some who think it may have occured elsewhere, and life was subsequently transferred to Earth from that location.

Possible locations for abiogenesis include Mars, Venus, Ceres, Europa, Titan, Enceladus... the list goes on, with decreasing amounts of probability in each case.

As I've said elsewhere on this forum, ballistic panspermia is unlikely (some might say very unlikely, and I wouldn't disagree), but it is not against the mainstream. Something can be both unlikely and mainstream.

[Colin Robinson]

I just want to add this, then I think I'm more or less done with this topic again.

Observation: Methane on Mars...
a) Hypothesis: ...indicates life.
b) Hypothesis: ...indicates volcanic activity.
c) Hypothesis: ...indicates "recently" exposed methane ice.
d) Hypothesis: ...indicates some other phenomenon we haven't observed yet.

While the highly improbable but highly desirable Hypothesis A would be the ultimate in discoveries, it in no way diminishes the importance and "Wanna know right now; when does the probe get there? Get it there faster, NASA!" factor of all three other possibilities.

Just sayin'.

For anyone who doesn't already know this, ESA and NASA are working together on a mission to Mars involving an orbiter, a lander, and a rover or two, whose objectives include tracking the methane and investigating its source. The project is called ExoMars, and is scheduled for 2016 - 2018.

[Trakar]

Also true, but we can't be certain what conditions were suitable for the formation of life, so we can't say much about the locations where it might be expected to emerge. Although we may assume with some confidence that abiogenesis occured on this planet at some point in the distant past, there are some who think it may have occured elsewhere, and life was subsequently transferred to Earth from that location.

Possible locations for abiogenesis include Mars, Venus, Ceres, Europa, Titan, Enceladus... the list goes on, with decreasing amounts of probability in each case.

As I've said elsewhere on this forum, ballistic panspermia is unlikely (some might say very unlikely, and I wouldn't disagree), but it is not against the mainstream. Something can be both unlikely and mainstream.

well beyond 2 standard deviations, IMO.

[Trakar]

I don't see what the big deal is here anyway. If the current evidence is not conclusive, then that means that we cannot yet conclude that we have evidence of ET.
In any case, if such conclusive evidence is eventually found, does the process by which we arrived at that evidence really matter? I think not. It doesn't matter whether we take a random guess, theorize, speculate (unfounded or founded) or flip a coin in order to discover conclusive evidence of ET. So what is needed in order to discover ET is a powerful heuristic, and this does not necessarily include having a correct theory of ET beforehand.

You well illustrate my point.

[Paul Beardsley]

I'd disagree with what you determine to be "clear," especially when the users of the language seem to be insisting on casual understandings and interpretations rather than employing stricter, and more proper scientific qualifications, only begrudgingly acknowledge the range of actual science evidences when dragged to them, and then use such casually misstated arguments in the support of assertions that are quite simply unsupported by the evidences (eg "Evidence for ET is mounting daily"). The word doesn't cause "bristling," the repeated and continuing context of its misusage and misapplication can, however, have that effect on some people.

This may have been true at the beginning of the thread, but the recent posts by Paul Wally, Colin Robinson and myself have shown appropriate caution.

As Jeff pointed out, the real eyebrow-raiser is the criticism of the expression "consistent with". (No, Jeff didn't refer to it as an eyebrow-raiser, but my phrasing is consistent with what he said.)

There seems to be a "skepticaller than thou" attitude in certain quarters. Evidence doesn't have to be conclusive to serve as a lead. If police find fingerprints on a murder weapon, they interview the suspect. They do not have to present alternative explanations for how come the fingerprints came to be there, any more than they have to present non-life explanations for methane on Mars. The fingerprints don't necessarily mean the suspect is the murderer, but they don't ignore it just because there might be another reason for them being there.

[Paul Wally]

You well illustrate my point.

This can be ambiguously interpreted. Either, I've now said something that you finally agree with or it confirms what you have been saying the whole time. I'll assume the latter interpretation as the more likely one.

I think that you think that the process matters as far as conclusive evidence is concerned. You think that, working on a certain unproven assumption somehow biases the result, but I don't see how that can possibly happen with conclusive evidence of the existence of something. We don't create evidence, we discover it. I see nothing wrong in saying what if there is life under such and such conditions and then carrying on with that assumption as if true with the eventual aim of checking whether in fact it is true. The whole point of making unproven assumption is not to believe it, but in fact, to test whether or not it is true.

I hope this makes things clearer.

[Colin Robinson]

I do. See how it would change us, I mean.

Think back... The (widespread) knowledge that the sky isn't an overturned bowl changed us forever. The repeated discoveries that we're not really the center of anything in time and space, except our own ignorance, helped bring about radical and progressive changes in how we think about ourselves and how we interact with the world. Changes that were invariably met with a great deal of kicking, screaming, upheaval and death (both real and threatened). A very large fraction of the world's population is wailing incessantly over the notion that we've distant common ancestry with every other critter on the planet. We're still choking on the notion that we've common ancestry with ourselves.

If scientific discoveries have not changed us, why all the fuss?

No, our science is dragging us into the future by the scruffs of our necks, sweeping along the unwilling with each next discovery that reveal how we're a much smaller player in a much _much_ larger universe than we've ever imagined possible. This is necessary, if uncomfortable and humbling, and ultimately the very best thing for us.

Well said!


... I just think it's important to let the science educate us in its time, and not anticipate its revelations.

I agree it is important not to jump to conclusions – either positive (e.g. life on Mars) or negative (e.g. no life on Mars)...

[WayneFrancis]

Regarding the emotional aspect, I think a lot of people share my stance: I really, really want there to be life out there, and I really want to know for certain that there is life out there. However, above all else I want the truth, even if it isn't the truth I hoped for. I don't want to pretend that something is evidence when it is not. I will not grasp at straws!

I actually feel hatred for the sort of UFO proponent who deliberately mischaracterises skeptics such as myself as being closed-minded and opposed to the idea of there being life. We are not in denial; when real evidence is found, it will be impossible to deny.

C

[Paul Beardsley]

C

?

[astromark]

Properly qualified remarks are rarely misunderstood or misinterpreted.

Oh my word... have you seen what I see...? and I see it so often. Its alarming..

We have a cor um of agreement here.

That as no such trace has yet been confirmed as real no such conclusion is possible..

That is not based on a belief structure but real and active science.

any other point is less than science. So for me is less than true. Awaiting confirmation.

[IsaacKuo]

?
If you have the font "Wingdings" on your computer, and if your web browser is set to allow the web page to choose its own fonts, then this "C" looks like a thumbs up symbol. If not, then it looks like a capital "C".

[Paul Beardsley]

Thanks for the explanation, Isaac.

And thanks for the thumbs up, Wayne, even if it was just a big C on my machine!

[Trakar]

This can be ambiguously interpreted. Either, I've now said something that you finally agree with or it confirms what you have been saying the whole time. I'll assume the latter interpretation as the more likely one.

I think that you think that the process matters as far as conclusive evidence is concerned. You think that, working on a certain unproven assumption somehow biases the result, but I don't see how that can possibly happen with conclusive evidence of the existence of something. We don't create evidence, we discover it. I see nothing wrong in saying what if there is life under such and such conditions and then carrying on with that assumption as if true with the eventual aim of checking whether in fact it is true. The whole point of making unproven assumption is not to believe it, but in fact, to test whether or not it is true.

I hope this makes things clearer.

Process not only can bias results, it is corruption of the processes of science that spawn pseudoscience,...or perhaps more appropriately, it is the hallmark of pseudoscience to twist and distort the processes of science to derive predetermined results based upon predillection rather than being led to understandings and theories by the verifieable evidences. When people begin shunning the processes of science and attempting to broaden the discussion to encourage more speculative possibilities rather than limiting themselves to the proper scientific definitions and evidences, then we have to be extremely vigilant not to leave mainstream science behind and skip across the boundary into fiction.

[Trakar]

Well said!

I agree it is important not to jump to conclusions – either positive (e.g. life on Mars) or negative (e.g. no life on Mars)...

What is the reasonable default condition? No apparent life, or, abundant hidden life?

[IsaacKuo]

What is the reasonable default condition? No apparent life, or, abundant hidden life?

Right now, we lack sufficient data to form a reasonable default condition. The problem has to do with liquid water conditions. EVERY place we have looked which has liquid water conditions has had life. But if Mars has liquid water conditions, those conditions are far enough underground that they are indeed hidden from us--so far. None of our probes have had to do more than literally scratch the surface.

There have been numerous environments in Earth where we thought life was impossible, but it has turned out to exist in all of the ones with liquid water conditions anyway. Since life on Earth seems to exist everywhere that liquid water conditions exist, it would be very interesting to finally explore somewhere outside of Earth with liquid water conditions. That first exploration may be some sort of digger that explores deep into Mars, or Europa, or some other planet/moon. Or it might be careful study of rocks or ice which displayed firm evidence of having recently been in liquid water conditions (a short enough time so we could reasonably find the remains of soft creatures).

Until that first data, we are in a situation where it's presumptive to have a default condition. We simply have too little data.

[Trakar]

Right now, we lack sufficient data to form a reasonable default condition. The problem has to do with liquid water conditions. EVERY place we have looked which has liquid water conditions has had life. But if Mars has liquid water conditions, those conditions are far enough underground that they are indeed hidden from us--so far. None of our probes have had to do more than literally scratch the surface.

There have been numerous environments in Earth where we thought life was impossible, but it has turned out to exist in all of the ones with liquid water conditions anyway. Since life on Earth seems to exist everywhere that liquid water conditions exist, it would be very interesting to finally explore somewhere outside of Earth with liquid water conditions. That first exploration may be some sort of digger that explores deep into Mars, or Europa, or some other planet/moon. Or it might be careful study of rocks or ice which displayed firm evidence of having recently been in liquid water conditions (a short enough time so we could reasonably find the remains of soft creatures).

Until that first data, we are in a situation where it's presumptive to have a default condition. We simply have too little data.

Observations and evidence determine default

We observe and see no evidence of life on Mars, that is the reasonable default condition.

The default might be incorrect and that is a situation which would demand correction if there is evidence to indicate otherwise.

I have sealed containers of deionized water that contain no apparent or detectable life sitting on my desk, your proposal that everywhere we find liquid water, we find life, would seem to require some adjusting.

[IsaacKuo]

We observe and see no evidence of life on Mars, that is the reasonable default condition.

Based on what we know, our observations are just as consistent that there is life on Mars. It's not enough for you to present one explanation and say this must therefore be the default explanation. You must compare it to other explanations and see if your explanation is a BETTER explanation.

Right now, based on what we know, it's an even balance of lack of information.


I have sealed containers of deionized water that contain no apparent or detectable life sitting on my desk, your proposal that everywhere we find liquid water, we find life, would seem to require some adjusting.

Certainly it's possible to kill natural life to create an artificial "environment", but we do not expect by default that someone has sterilized Mars.

Suppose I tell you that I have a glass of water on my desk. Do you think there is life in that glass of water? You have not detected any life in this glass of water. Should your default assumption be that there is no life in it?

Suppose I give you more data--suppose I tell you that I have looked at this glass of water very closely, and I don't see any signs of life. Okay, maybe my eyesight isn't good enough to see microscopic life forms (if microscopic life forms exist), but surely this is strong evidence that there is no life in that glass of water! Right?

[Paul Wally]

Process not only can bias results, it is corruption of the processes of science that spawn pseudoscience,...or perhaps more appropriately, it is the hallmark of pseudoscience to twist and distort the processes of science to derive predetermined results based upon predillection rather than being led to understandings and theories by the verifieable evidences. When people begin shunning the processes of science and attempting to broaden the discussion to encourage more speculative possibilities rather than limiting themselves to the proper scientific definitions and evidences, then we have to be extremely vigilant not to leave mainstream science behind and skip across the boundary into fiction.

This sounds like a rather general dogmatic creed about what you believe science should be, without giving any examples nor providing any rational argument for it. Please describe a scenario where conclusive evidence can be a biased result. It really looks like a logical impossibility to me. It's like saying if Opportunity observes lifeforms with it's micro-imager, then it's a biased result because they speculated that there is life on Mars before having the evidence. If evidence is as theory laden as you imply, not only would evidence stand on very shaky ground, the word "discover" loses all it's meaning. That's why I'm saying it doesn't matter what you believe, speculate, theorize or guess beforehand, whatever you discover will be the judge of whether your hypothesis is true.

And I think you misunderstand the concept of verifiability . As far as logical positivism goes, the concept of verifiability applies to propositions (theoretical statements). "There is life on the Moon" is a verifiable proposition, because we can go and verify empirically whether in fact it is true. "There is a reality beyond what we can measure" is not a verifiable proposition, according to logical positivism. If something is verifiable then it is merely potentially verified, so "verifiable evidences" reads "potentially verified evidences". All evidences are verified, if it's not verified then it's not yet evidence.

[Colin Robinson]

What is the reasonable default condition? No apparent life, or, abundant hidden life?

If by "apparent life" you mean macroscopic life, then I'd agree it is reasonable to conclude Mars doesn't have that. If there were forests or cities there, we would have detected them. (Unless they were in the "invisible elf" category!)

Microscopic life is another question.

The possibility that a planet might lack macroscopic life, but nonetheless have micro-organisms, is not science fiction but mainstream science. The Earth itself seems to have been like that for several billion years -- most of its history.

Detecting microscopic organisms presents a challenge, not because they are hidden, or invisible, but just because they are small.

All the same , there are several feasible strategies for finding them, if they are either there now, or have been in the past. One strategy has been mentioned by Isaac Kuo -- follow the water.


Since life on Earth seems to exist everywhere that liquid water conditions exist, it would be very interesting to finally explore somewhere outside of Earth with liquid water conditions. That first exploration may be some sort of digger that explores deep into Mars, or Europa, or some other planet/moon. Or it might be careful study of rocks or ice which displayed firm evidence of having recently been in liquid water conditions (a short enough time so we could reasonably find the remains of soft creatures).

Another strategy for finding micro-organisms is to track down stuff that may have been produced by them -- e.g. follow the methane. As ExoMars is intended to do.

Another strategy is to look for the stuff microbes are made of -- follow the complex organic molecules.

I know Viking tried to do that, but it is no longer considered to have produced a reliable negative result. Next year the Curiosity rover will have another go at looking for organics.

Until Mars has been thoroughly investigated using strategies like these, I agree with Isaac.

It is simply too early to talk about a default position re small living organisms on Mars.

[Trakar]

If by "apparent life" you mean macroscopic life, then I'd agree it is reasonable to conclude Mars doesn't have that. If there were forests or cities there, we would have detected them. (Unless they were in the "invisible elf" category!)

Microscopic life is another question...


Not at all, microscopic life on the earth is still one of life's most apparent expressions. The life that has existed for billions of years, early on significantly and obviously altered the chemistries and compositions of our planet's atmosphere and surface layers.

Ambiguous methane wisps notwithstanding, Mars offers nothing suggestive of billions of years of evolutionary adaptation of a proliferate expression of life as we know it, which is arguably a chief characteristic of life as we know it,...obvious and aggressive expansion and adaptation into any and all available niches of energy exploitation. It may turn out that there are deep rock organisms eeking out an existence somewhere in the Martian lithosphere, but the existence of such, currently, isn't much more dependable or verifiable than the transparent Kiblerites you mention.

[Paul Wally]

It may turn out that there are deep rock organisms eeking out an existence somewhere in the Martian lithosphere, but the existence of such, currently, isn't much more dependable or verifiable than the transparent Kiblerites you mention.

Of course it's not dependable, because we cannot depend on what has not been observed, but it is definitely verifiable. An invisible (Martian) elf is an example of something that is not verifiable. Visible elves on the other hand are verifiable. They're just not verified. There's a difference between "verifiable" and "verified".

[iquestor]

Not at all, microscopic life on the earth is still one of life's most apparent expressions. The life that has existed for billions of years, early on significantly and obviously altered the chemistries and compositions of our planet's atmosphere and surface layers.

Ambiguous methane wisps notwithstanding, Mars offers nothing suggestive of billions of years of evolutionary adaptation of a proliferate expression of life as we know it, which is arguably a chief characteristic of life as we know it,...obvious and aggressive expansion and adaptation into any and all available niches of energy exploitation. It may turn out that there are deep rock organisms eeking out an existence somewhere in the Martian lithosphere, but the existence of such, currently, isn't much more dependable or verifiable than the transparent Kiblerites you mention.

Actually many scientist beleive that life here on earth started as a deep biosphere, using geothermal heat and chemical energy first, then later moved to the surface. I think its possible there is a deep biosphere on mars we havent detected, except through those methane 'wisps'....

[Trakar]

Actually many scientist beleive that life here on earth started as a deep biosphere, using geothermal heat and chemical energy first, then later moved to the surface. I think its possible there is a deep biosphere on mars we havent detected, except through those methane 'wisps'....

I find no compelling reason to believe Martian methane to be biogenic in origin.

"Geology of possible Martian methane source regions" -
http://www.sciencedirect.com/science/article/pii/S0032063310001443

"Methane on Mars: A Perspective from Earth"
http://www.searchanddiscovery.com/abstracts/pdf/2011/hedberg-beijing/abstracts/ndx_schoell02.pdf

[Colin Robinson]

Not at all, microscopic life on the earth is still one of life's most apparent expressions. The life that has existed for billions of years, early on significantly and obviously altered the chemistries and compositions of our planet's atmosphere and surface layers.

What was so obvious about the way early microscopic life altered our planet's chemistry?

Earlier in this thread, you mentioned the free oxygen in Earth's atmosphere.


The sustained high level of free oxygen is a strong biosignature, probably the most compelling argument for life on our planet from afar.

However, as I understand it, oxygen first started to build up in the atmosphere about 2.4 billion years ago -- about 1 billion years after life got started. Is that what you call "early on"?

Before that, oxygen was already being produced, but it was reacting with elements such as iron to form oxides. So, yes, there were changes to the chemistry of surface layers.

But is the presence of iron oxides on a planetary surface an obvious sign of life?

[R.A.F.]

...is the presence of iron oxides on a planetary surface an obvious sign of life?

Is there a reason why it would be?

[Colin Robinson]

Why would it be?

Because Trakar just told us that the chemical manifestations of microscopic life here on Earth were both early and obvious…

[R.A.F.]

I see...





edit to add....just to be "clear", I am not agreeing, or disagreeing, I am simply acknowledging that I read what you have posted. :)

Thank you...

[Trakar]

What was so obvious about the way early microscopic life altered our planet's chemistry?

Earlier in this thread, you mentioned the free oxygen in Earth's atmosphere.


I mentioned free atmospheric oxygen, as the most obvious current indication of life on our planet.



However, as I understand it, oxygen first started to build up in the atmosphere about 2.4 billion years ago -- about 1 billion years after life got started. Is that what you call "early on"?


Well, yes, yes I do! At least when we are talking about the creation of life and the proliferation and evolution of that life to the point where it has expanded throughout the range of its biome. That aside, it is generally considered disingenuous (at the least) to take two different statements based upon two different condition sets and then conflate them so as to make it seem as though a person was making them in regards to the same condition set.



Before that, oxygen was already being produced, but it was reacting with elements such as iron to form oxides. So, yes, there were changes to the chemistry of surface layers.


I wouldn't limit myself to the considerations this single reaction and product, and remember, I did say: "The life that has existed for billions of years, early on significantly and obviously altered the chemistries and compositions of our planet's atmosphere and surface layers."


But is the presence of iron oxides on a planetary surface an obvious sign of life?

on its own and under all conditions, of course not. Oxygen is fairly abundant and there are many abiogenic circumstances under which water (and most other oxygen compounds) can be induced to decompose. Metals like iron do tend to grab onto it with some vigor. Substantive, and sustained ratios of free O2 indicates a complex, regular oxygen cycle in progress, which is a good indicator of the presence of life. But that is more in reference to an advanced state of development.

What I was thinking of in reference to the atmosphere, at least initially, was the biogenic methane component. Which, BTW, may well have been much more responsible for much, if not most, of the thorough oxidation of surface soils and waters. These high, largely biogenic, methane levels may have strongly influenced the oxygen content - Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth (http://www.ncbi.nlm.nih.gov/pubmed/11486082) - of our early atmosphere. These levels of methane, this deep into the solar well (Titan is about the closest analog-aside from it's temperature), seems to have been suspiciously high, even for a big planet with a lot of tectonic activity ("A coupled atmosphere–ecosystem model of the early Archean Earth (http://www3.geosc.psu.edu/~jfk4/PersonalPage/Pdf/Geobiology_05.pdf)".).

I'm sure I've discussed other such life indicators in other discussions here and elsewhere. But we can bring them out for a revisit if you'd like. Of course, very few of them are compelling by themselves, but when there are many of them expressed in the same planet, (or as in the case of the Earth, all of these indicators at once) then the life solution becomes a much more compelling and reasonable explanation. A few trace whisps of methane in the modern Martian atmosphere do not resemble this situation.

[Colin Robinson]

What I was thinking of in reference to the atmosphere, at least initially, was the biogenic methane component. Which, BTW, may well have been much more responsible for much, if not most, of the thorough oxidation of surface soils and waters. These high, largely biogenic, methane levels may have strongly influenced the oxygen content - Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth (http://www.ncbi.nlm.nih.gov/pubmed/11486082) - of our early atmosphere. These levels of methane, this deep into the solar well (Titan is about the closest analog-aside from it's temperature), seems to have been suspiciously high, even for a big planet with a lot of tectonic activity ("A coupled atmosphere–ecosystem model of the early Archean Earth (http://www3.geosc.psu.edu/~jfk4/PersonalPage/Pdf/Geobiology_05.pdf)".).

I'm sure I've discussed other such life indicators in other discussions here and elsewhere. But we can bring them out for a revisit if you'd like. Of course, very few of them are compelling by themselves, but when there are many of them expressed in the same planet, (or as in the case of the Earth, all of these indicators at once) then the life solution becomes a much more compelling and reasonable explanation. A few trace whisps of methane in the modern Martian atmosphere do not resemble this situation.

It's true that even today, the level of methane in Earth's atmosphere is a lot higher than for Mars. If Mars does have a population of methanogenic organisms, it would have to be a small population.


(Titan is about the closest analog-aside from it's temperature)

Very true.

Not only does Titan have a lot more methane than Mars, but the indications are that methane is being produced (or, strictly speaking, regenerated) on a much bigger scale.

If it does turn out that both Titanian and Martian phenomena are due to methanogenic life, the living things on Titan would logically be much more abundant and/or much more active, in comparison with those on Mars.

[Trakar]

...If it does turn out that both Titanian and Martian phenomena are due to methanogenic life, the living things on Titan would logically be much more abundant and/or much more active, in comparison with those on Mars.

The difference is that Titan formed out near the ice zone so it was formed with a lot of native methane, it isn't being "produced" so much as merely cycling (much like water on Earth).

[Colin Robinson]

The difference is that Titan formed out near the ice zone so it was formed with a lot of native methane, it isn't being "produced" so much as merely cycling (much like water on Earth).

I agree there are distinct analogies between what happens with methane on Titan, and what happens with water on Earth. But why the word "merely"?

Water on Earth cycles in at least two senses. There is the meteorological cycle of evaporation and precipitation, and there is the chemical cycle, where water molecules are broken up in photosynthesis, and new water molecules get formed in respiration.

Similarly on Titan. There is the meteorological cycle -- methane rain forming rivers and lakes.

There also seems to be a chemical cycle -- photolysis in the upper atmosphere strip the methane of its hydrogen, enabling the formation of acetylene (for instance), as well as much larger organic molecules. Then, at or near the surface (according to findings reported in June last year), there are indications that methane gets reconstituted by a reaction between acetylene and hydrogen.

That is the most interesting bit, because the acetylene-hydrogen reaction implies a powerful unknown catalyst, or group of catalysts, whose role in the cycle is like the role of enzymes in the chemical cycles on Earth...

[marsbug]

I find no compelling reason to believe Martian methane to be biogenic in origin.

"Geology of possible Martian methane source regions" -
http://www.sciencedirect.com/science/article/pii/S0032063310001443

"Methane on Mars: A Perspective from Earth"
http://www.searchanddiscovery.com/abstracts/pdf/2011/hedberg-beijing/abstracts/ndx_schoell02.pdf

I may not express this thought well: At this point is there a compelling reason to believe it is the result of geochemistry or the decomposition of clatherates? Unless there is evidence (there may be and I'm just unaware of it) that is more consistent with one hypothesis than the rest then shouldn't we be suspending judgement - whilst keeping an open and unbiased mind to all the possibilities?

[Trakar]

I agree there are distinct analogies between what happens with methane on Titan, and what happens with water on Earth. But why the word "merely"?...


Aside from some as yet unsubstantiated speculation, I've seen no compelling evidence suggesting that any of Titan's methane is biogenic in origins. And there are some rather persuasive arguments against that concept.

"The significance of trace constituents in the solar system," - http://www-personal.umich.edu/~atreya/Articles/atreya_Faraday.pdf


...Even if the above scenario works, it would not be responsible for the origin of methane on Titan, because in order for the bacteria to generate methane, they need methane in the first place as the nutrients, C2H2 + 3H2, are photochemical products of methane.8 Titan’s methane must have another origin. Whether or not methanogens are present on Titan is another matter. If they did exist, they would
severely deplete the nutrients, H2 and C2H2. The Huygens GCMS determines a uniform mole fraction of 0.001 for H2,46 in good agreement with the Cassini Composite Infrared Radiometer Spectrometer value18 and the Voyager value,17 as well as various photochemical models according to which H2 arises from CH4 and is expected to be uniformly mixed because of its one million year lifetime in Titan’s atmosphere. Furthermore, the Huygens GCMS detected acetylene (amongst other molecules) evaporating from Titan’s surface in the measurements made for over an hour after the probe landed. Thus, no perceptible depletion in the nutrients,
C2H2 and H2, is recorded, which argues against widespread methanogenic life in Titan’s surface, at least in the Huygens landing site, as was suspected previously from preliminary analysis of the Cassini-Huygens data.
...

http://books.google.com/books?id=CBx9KDH1qaYC&printsec=frontcover&dq=Titan+from+Cassini-Huygens&hl=en&src=bmrr&ei=WimaTo_JHcebiAL8zaS7DQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CDIQ6AEwAA#v=onepage&q&f=false

But pleae, don't get me wrong, If Titan were substantially larger and warmer, I would consider it a much more interesting and potential cradle for life.

[Colin Robinson]

Aside from some as yet unsubstantiated speculation, I've seen no compelling evidence suggesting that any of Titan's methane is biogenic in origins. And there are some rather persuasive arguments against that concept."The significance of trace constituents in the solar system," - http://www-personal.umich.edu/~atreya/Articles/atreya_Faraday.pdf

The "rather persuasive" paper you've mentioned makes a couple of points.

It says that formation of methane out of acetylene and hydrogen would not account for the origin of methane there, because acetylene on Titan is formed from methane.

This is true enough. If there are methanogens on Titan, they are not adding methane to a formerly methane-less environment, they are enabling a cycle where methane is broken up high in the atmosphere, then reconstituted at the surface.

It also says that the acetylene and hydrogen levels on Titan seem not to be consistent with the hypothesis of methanogenic life there.

As far as I know, the most up-to-date analyses of acetylene and hydrogen levels in Titan's atmosphere are:

1. Roger N. Clark et al, "Detection and Mapping of Hydrocarbon Deposits on Titan", JGR 2010.
2. Darrell Strobel, "Molecular Hydrogen in Titan's Atmosphere", Icarus 2010

For a summary of Clark's and Strobel's 2010 findings, Chris McKay's article, Cassini: Making Sense of the News - Have we discovered evidence for life on Titan? (http://www.ciclops.org/news/making_sense.php?id=6431&js=1)

The levels of hydrogen and acetylene reported by Clark and Strobel are consistent with the methanogen hypothesis. And yes, they are also consistent with the alternative hypothesis that the hydrogen and acetylene are being transformed into methane by an unknown non-living catalyst.

Now, it is quite conceivable that Clark's work and/or Strobel's work will get refuted at some point in the future.

But the paper you've quoted by Sushil Atreya is not a refutation of Clark nor of Strobel. As far as I can see, it actually doesn't refer to their findings at all. It is a general discussion of methane and nitrogen in the solar system, and its information about Titan comes from less up-to-date specialist articles.

[Trakar]

...But the paper you've quoted by Sushil Atreya is not a refutation of Clark nor of Strobel. As far as I can see, it actually doesn't refer to their findings at all. It is a general discussion of methane and nitrogen in the solar system, and its information about Titan comes from less up-to-date specialist articles.

The intent wasn't to refute Clark merely to demonstrate more of the mainstream consideration with regards to the methane cycle of Titan. As Chris McKay stated in his interview with Universe Today back in June of 2010, in reference to these two papers, that life on Titan is “certainly the most exciting, but it’s not the simplest explanation for all the data we’re seeing.” I'm not interested in snark or attitude, I think the discovery of exolife is probably one of the most important in all of science, but it is something that must actually be discovered not blindly accepted or gleefully promoted from ambiguity and the lack of compelling supportive evidences.

[Colin Robinson]

The intent wasn't to refute Clark merely to demonstrate more of the mainstream consideration with regards to the methane cycle of Titan. As Chris McKay stated in his interview with Universe Today back in June of 2010, in reference to these two papers, that life on Titan is “certainly the most exciting, but it’s not the simplest explanation for all the data we’re seeing.” I'm not interested in snark or attitude, I think the discovery of exolife is probably one of the most important in all of science, but it is something that must actually be discovered not blindly accepted or gleefully promoted from ambiguity and the lack of compelling supportive evidences.

I agree with your statement that "the discovery of exolife is probably one of the most important in all of science".

Chris McKay is right to describe the scenario of life on Titan as "most exciting"...

He is also right to point out that life is not the simplest hypothesis consistent with the data.

When considering an atmospheric anomaly in a world about which we still know little, life is unlikely to be the simplest explanation ever.

Even, if, for instance, free oxygen is found in the atmosphere of an exoplanet. Living things are, after all, the most complex of natural systems. And oxygen can be produced by volcanos...

[Paul Wally]

The thing is that we're not trying to explain the methane, like we're trying to explain sunspots or some or other interesting anomaly. I.e. it's not the kind of research program where we are trying to explain something. It's a program of searching for something, in this case we are searching for life. So the issue of the simplest explanation is not really relevant, because as I said, we're not trying to explain anything here. It's like a mining company prospecting for oil, or gold or platinum. Same situation here, we're prospecting for life, and we follow the leads where we may possibly find life, even if the chances seem slim, it's worth trying.

[Colin Robinson]

The thing is that we're not trying to explain the methane, like we're trying to explain sunspots or some or other interesting anomaly. I.e. it's not the kind of research program where we are trying to explain something. It's a program of searching for something, in this case we are searching for life. So the issue of the simplest explanation is not really relevant, because as I said, we're not trying to explain anything here. It's like a mining company prospecting for oil, or gold or platinum. Same situation here, we're prospecting for life, and we follow the leads where we may possibly find life, even if the chances seem slim, it's worth trying.

I agree that it is important to follow up leads, if we want to know about life beyond Earth. To look where scientists think life is plausible, whether or not they think it probable.

It is important to remember that the hypothesis Titan could have some form of life was conceived before the June 2011 findings, which were consistent with the hypothesis.

To put it another way, the data about hydrogen and acetylene was not the first reason for thinking that Titan might have life; rather, an additional reason.

[whimsyfree]

(AP) -- Lately, a handful of new discoveries make it seem more likely that we are not alone - that there is life somewhere else in the universe.

This optimism, it's infectious!


None of those discoveries has much if anything to do with extraterrestrial life. It seems more like an infection of wishful thinking than optimism.

[mutleyeng]

its been interesting reading peoples views in this and the other similar (really long) thread.
going back to the article originally referenced, reading peoples views it made me wonder just what evidence could be found to make the alien hypothesis less likely.
As paul Davies said in his book, the erie silience, 30 or 40 years ago it would be considered a bit crackpot to talk about alien life in a serious scientific environment, today it is mainstream....but nothing has really changed in the science. we still only have one example of life no matter how much more hardy it is than we first thought.

we seemed to have reached a point now where the alien hypothesis is unfalsifiable....not just in popular culture, but within mainstream science
added...ok, it always was, but i guess im talking about the way it is presented

[Selfsim]

we seemed to have reached a point now where the alien hypothesis is unfalsifiable....not just in popular culture, but within mainstream science
added...ok, it always was, but i guess im talking about the way it is presented
With Empirical Testing, the wording and scoping, is essential.
An hypothesis is verifiable, or falsifiable, in theory, as long as testing it doesn't violate any Physical Principles. In this case, using the particle horizon as a boundary is vital ...

i) In this case, tests performed inside the observer's particle horizon are theoretically verifiable and falsifiable, whereas tests performed outside the horizon are not.

ii) Scoping the tests so they are limited to within the observable universe, thus eliminates the assured theoretical non-verifiability and non-falsifiability, for tests performed outside of it.

iii) The hypothesis: "Earth-like exo-life does not exist in the observable universe": is falsifiable in theory. This is because biological tests for Earth-like life exist without violating any Laws of Physics, and it would take just one exo-discovery of it, to be falsified. However, it may not be falsified in practice if life is a rarity, because full coverage of the search-space is impractical. The existence of the possibility of a chance discovery, no matter how small, also renders the hypothesis as theoretically falsifiable.

iv) If this hypothesis is falsifiable in theory, the conjugate must also be verifiable theory, ie: "Earth-like exo-life does exist in the observable universe". However, it may not be verified in practice, if life is a rarity, because full coverage of the search-space is impractical. Chance discoveries also render this hypothesis as theoretically verifiable.

v) My own view is that I choose to live inside the real universe. This universe is, (unfortunately), limited by practicality boundaries, as is the bulk of the empirical physical testing sciences.

vi) Earth-like exo-life testing, relies on biological tests developed for Earth-life. It thus falls well within the scope of empirical testing principles. The 'rules' of practicality thus ultimately determine the feasibility or non-feasibility of Earth-like exo-life testing.

Regards

[mutleyeng]

thats what i said

[Colin Robinson]

its been interesting reading peoples views in this and the other similar (really long) thread.
going back to the article originally referenced, reading peoples views it made me wonder just what evidence could be found to make the alien hypothesis less likely.
As paul Davies said in his book, the erie silience, 30 or 40 years ago it would be considered a bit crackpot to talk about alien life in a serious scientific environment, today it is mainstream....but nothing has really changed in the science. we still only have one example of life no matter how much more hardy it is than we first thought.

we seemed to have reached a point now where the alien hypothesis is unfalsifiable....not just in popular culture, but within mainstream science
added...ok, it always was, but i guess im talking about the way it is presented

What evidence could be found to make the alien hypothesis less likely? Perhaps it depends exactly which "alien hypothesis" you have in mind. The hypothesis that there is alien life somewhere else in the universe? Or the hypothesis that there are alien organisms close enough for us humans to find them?

The hypothesis that there is life somewhere else in the universe is indeed very difficult to falsify. Even so, I think it would be seen as less likely

* if it could be shown that planet Earth is radically exceptional – that there is something about our planet's position or composition that is essential for life, and that no other world, anywhere in the universe is likely to match.

or

* if it could be shown that even on an Earth-like world, emergence of life is an event of extremely low probability, therefore unlikely to be repeated.

The hypothesis that there are alien organisms close enough for us humans to find them is a different matter. Around 30 years ago, scientists such as Norman Horowitz thought it had already been almost falsified -- i.e. shown to be extremely unlikely. His view was based on:

* results of the Viking mission to Mars
* no plausible habitat for life in the solar system other than Mars
* at that time, no extra-solar planets known

A lot has changed in the science. There are now several plausible habitats for alien life in this solar system: place where alien organisms could, in theory live. The hypothesis that there are alien organisms even in this solar system has not be falsified.

What possible future evidence could make it less likely?

* If, in the future, study of Mars shows that the small but intriguing amount of methane there is due to some non-biological process.
* If landers on Europa show that it doesn't have underground liquid water after all. Or, it does have liquid water, but sampling of the water shows no signs of life.
* If further exploration of Titan shows either shows that compounds like acetylene are not decaying into methane. Or, if they are, the decay is found to be caused by a mineral catalyst rather than an organism.

How's that for a start?

[djellison]

Just a reminder - there is, to date, no direct evidence of any ET life whatsoever.

There is evidence for an increasing catalogue of places where life might occur - but no evidence whatsoever of ET life itself.

[Colin Robinson]

Just a reminder - there is, to date, no direct evidence of any ET life whatsoever.

There is evidence for an increasing catalogue of places where life might occur - but no evidence whatsoever of ET life itself.

If there are organisms swimming about in Europa's underground ocean, do you think they have any evidence whatsoever of life on Earth?

[Paul Beardsley]

If there are organisms swimming about in Europa's underground ocean, do you think they have any evidence whatsoever of life on Earth?

I'm curious about the relevance of this. Evidence (or its lack) is concerned with knowing if something exists or not.

Fifty years ago there was no evidence of extrasolar planets, although their existence seemed likely. Discovering them did not alter their objective reality, it was merely an addition to our knowledge.

I picture a dialogue box that asks, "Do X exist?" and gives the two tick boxes "Yes" and "No". You can click neither or one, but not both. For "Do horses exist?" we can confidently click Yes; for "Do centaurs exist?" we can confidently click No. For "Do extraterrestrials exist?" we can leave both boxes unticked.

I sometimes get the feeling that a certain kind of mindset cannot understand this third option; worse, some appear to believe that the choice to leave both boxes unticked somehow equates to ticking the other box. For instance, a man who clicks Yes to "Do extraterrestrials exist?" is inclined to think that the woman who chose to leave both boxes blank is denying the existence of aliens.

[Selfsim]

If there are organisms swimming about in Europa's underground ocean, do you think they have any evidence whatsoever of life on Earth?With all due respect to djellison, he doesn't have to think about this !
And his thoughts are completely urelated, and irrelevant to physical evidence.
Regards

[Selfsim]

I sometimes get the feeling that a certain kind of mindset cannot understand this third option; worse, some appear to believe that the choice to leave both boxes unticked somehow equates to ticking the other box. For instance, a man who clicks Yes to "Do extraterrestrials exist?" is inclined to think that the woman who chose to leave both boxes blank is denying the existence of aliens.Absolutely agree, Paul ! I have encountered this effect myself, in the past !

All: Please excuse my previous post .. I noticed Paul's just after I posted mine .. our thoughts were the same, though.

Much of this speculation appears to me like word-play, as well.

Regards

[Paul Beardsley]

Thanks, Selfsim.

I think this thread would have been a lot less problematic if A.DIM had chosen a better title. The evidence for ET yesterday was zero; the evidence for ET today is also zero, so it's difficult to see how the evidence is mounting. However, if the title referred to the increasingly widespread prevalence of conditions that we think are conducive to life, that might have prompted a more scientific discussion.

[Colin Robinson]

I'm curious about the relevance of this.

I wanted to make the point that other worlds, such as Europa, are indeed other worlds.

Earlier in this thread, various people compared hypotheses about life beyond Earth with dragon's footprints in someone's backyard, invisible elves etc.

But Europa is not the backyard of any Earthling.


I picture a dialogue box that asks, "Do X exist?" and gives the two tick boxes "Yes" and "No". You can click neither or one, but not both. For "Do horses exist?" we can confidently click Yes; for "Do centaurs exist?" we can confidently click No. For "Do extraterrestrials exist?" we can leave both boxes unticked.

I sometimes get the feeling that a certain kind of mindset cannot understand this third option; worse, some appear to believe that the choice to leave both boxes unticked somehow equates to ticking the other box. For instance, a man who clicks Yes to "Do extraterrestrials exist?" is inclined to think that the woman who chose to leave both boxes blank is denying the existence of aliens.

I agree.

It is an open question whether or not living things exist on Mars, or Europa, or Titan.

It can't be answered without making the effort and spending the money to send out more space probes.

That's the thing about science. Until you actually do the experiment, you don't know what the result is going to be.

[mutleyeng]

I'm curious about the relevance of this. Evidence (or its lack) is concerned with knowing if something exists or not.

Fifty years ago there was no evidence of extrasolar planets, although their existence seemed likely. Discovering them did not alter their objective reality, it was merely an addition to our knowledge.

I picture a dialogue box that asks, "Do X exist?" and gives the two tick boxes "Yes" and "No". You can click neither or one, but not both. For "Do horses exist?" we can confidently click Yes; for "Do centaurs exist?" we can confidently click No. For "Do extraterrestrials exist?" we can leave both boxes unticked.

I sometimes get the feeling that a certain kind of mindset cannot understand this third option; worse, some appear to believe that the choice to leave both boxes unticked somehow equates to ticking the other box. For instance, a man who clicks Yes to "Do extraterrestrials exist?" is inclined to think that the woman who chose to leave both boxes blank is denying the existence of aliens.

thanks for this post Paul.
This is exactly what Paul Davies was trying to say.
The reason for my post was inspired by some chap many many post back that seemed to have quite an extreme certainty in his own mind, and kept asking the skeptics to name a scientist that didnt agree with him.
He kinda had a point.
For me both boxes remain firmly un-ticked.
Im sure it is true also for the scientist the other chap was refering to, but they dont seem to make much effort to present in that way.

[djellison]

With all due respect to djellison, he doesn't have to think about this !
And his thoughts are completely urelated, and irrelevant to physical evidence.
Regards

Well actually - it's rather related.

This thread title starts ' Evidence for ET is mounting'

Someone please provide a single piece of physical evidence for the existence of ET.

I'm yet to see any.

There is evidence for potential habitability. Evidence for 'building blocks' in many places. But of life itself? Not an iota of it.

Unless I'm very much mistaken.

The only answer to the question 'is there life elsewhere?' is

'Don't know'.

There is no direct evidence for it.

There is evidence that it might be possible.

But no evidence for it.

We need to go look for it.

[Colin Robinson]

Well actually - it's rather related.

This thread title starts ' Evidence for ET is mounting'

This thread title also says "but not proven".


Someone please provide a single piece of physical evidence for the existence of ET.

Please first explain what sort of thing you would consider "evidence".


There is evidence that it might be possible.

But no evidence for it.

We need to go look for it.

I agree that we need to go look.

The way the science has changed in the last 30 or so years is this… Right now we know of plausible places where we can look for it. Thirty years ago, (in the opinion of very prominent scientists like Lynn Margulis, Norman Horowitz) there seemed to be nowhere we could look.

[Selfsim]

Well actually - it's rather related.
… Hi djellison;
I didn't mean to speak on your behalf as an individual .. (apologies if it came across that way).
Cheers

[Selfsim]

… Right now we know of plausible places where we can look for it. Thirty years ago, (in the opinion of very prominent scientists like Lyn Margulis, Norman Horowitz) there seemed to be none.Colin;
Why not try considering that opinions are separate from physical reality?
The scientific process results in physical evidence … opinions of scientists (or anyone's), doesn't.
Regards

[djellison]

Please first explain what sort of thing you would consider "evidence".

Umm...evidence is evidence.

Not of habitability - of actual life

[transreality]

Please first explain what sort of thing you would consider "evidence".




specimens. fossils. incontrovertible images thereof.

[Colin Robinson]

Colin;
Why not try considering that opinions are separate from physical reality?
I have tried that already, actually.

The scientific process results in physical evidence … opinions of scientists (or anyone's), doesn't.

Don't they, now?

Where does the scientific process get its physical evidence?

It gets it from experiments and observations. Which are planned and conducted by scientists.

How do the scientists plan their experiments? They first form a view (an opinion) as to what sort of experiment has a chance of producing significant data, to support or falsify some hypothesis...

If the experiment does produce significant data, then yes, the opinions of the scientists who planned it have then resulted in physical evidence, either for or against something.

[Selfsim]

Where does the scientific process get its physical evidence?

It gets it from experiments and observations. Which are planned and conducted by scientists.

How do the scientists plan their experiments? They first form a view (an opinion) as to what sort of experiment has a chance of producing significant data, to support or falsify some hypothesis...

If the experiment does produce significant data, then yes, the opinions of the scientists who planned it have then resulted in physical evidence, either for or against something.I think you may be trivialising a tad, the contribution of a quite extensive process, (in the case of exo-life detection), which translates mere opinion, whilst maximising the quality of end results ... which can then cited as evidence.

But, then again, that would just be my mere opinion ... :)

Regards

[mutleyeng]

i do pretty much agree with the trust of your agument, but you really need to lighten up on those poor ol exo planets.
You may be right that it could never give answers to life with any reasonable certainty, but right now thats not what it is trying to do.
I think it will be many generations of space craft before we would ever be looking at one particular world with a watery mouth.
if ever there is such a target, maybe someone will pay for a Maccone gravitational lens program.
is our study of CMB physical evidence, or is it just evidence that fits predictions.
IT will be the same with exo planets i hope. we need lots of data so we can have models and be able to make predictions, then we need to build the hardware to see if those predictions hold true.
that is of course, just my opinion
selfism, if ever you have the inclination perhaps you could think about starting a thread where you put your case for why exo planet research is interfering with the progress of more potentially lucrative local research. I may be interpreting you wrong, but that seems to be your concern. It would be an interesting topic im sure

[djellison]

Where does the scientific process get its physical evidence?
.

Experimentation and observation.

You're playing a weird game of semantics here.

Let me flip it - you asked what I would consider sound evidence for ET life - what evidence are you suggesting (if indeed you are) we already have for ET life?

[KABOOM]

I think that the wording semantics flow in both directions in this admittedly "open question".

Many often repeat the refrain, "There is still not one single shred of evidence of life outside of Earth" (or something close to that).

This statement carries with it a certain air of definitiveness as if the question has been asked and answered (or almost exhaustively answered). The reality is that we are so far away from even beginning to scratch the surface of making a dent in the "evidence" that would be required to answer the question.

It is akin to looking at a newborn adopted infant (without any genetic testing) and stating things like, "there is not one single shred of evidence that this human will ever be able to hold a job", or "there is not one single shred of evidence that this human will become a self-made billionaire". Fine, true statements. But the infant is 7 days old. And when we all die that same infant may only be 11 days old.

[Paul Beardsley]

I'm not sure what that adds, KABOOM.

One doesn't normally apply evidence to infants like that. We know that a vast number of infants grow up to hold down jobs, and unless the infant in question is markedly different in some way (e.g. severely disabled), we'd say that, based on the life stories of similar "samples", it seems reasonably likely that the infant will one day have a job.

Where life-bearing worlds are concerned, we have a single example. We know that life in the wider universe is either non-existent, extremely common, or somewhere in between. There is no reason to choose one of these until we have more information.

[mutleyeng]

i just dont think thats a proper way to look at it Kaboom.
1. There is mounting evidence for ET life sustaining enviroments in the universe
2. there is mounting evidence for ET life.

the difference between these 2 is not semantics

[Colin Robinson]

specimens. fossils. incontrovertible images thereof.

That sort of incontrovertible evidence – also called proof – has not yet been found by terrestrial scientists. As I think you know...

So why has this thread gone on so long?

Because the word "evidence" has other meanings as well. People talk of weak evidence, circumstantial evidence, indirect evidence, inconclusive evidence.

It may not be as exciting as stronger evidence (proof). But the point is, if we follow up that weak evidence it will either lead to stronger evidence, or to falsification.

E.g. The atmosphere of Mars is now known to contain a small amount of methane. If we trace that methane to its source, we will either find

* the sort of proof you'd like -- living specimens of a Martian species of methanogen (methane-producing organism).OR
* we may find that a non-living process is producing the methane. In that case, the hypothesis that Mars has a population of methanogens will have been falsified.

[djellison]

I think that the wording semantics flow in both directions in this admittedly "open question".

Many often repeat the refrain, "There is still not one single shred of evidence of life outside of Earth" (or something close to that).

Which is true.


This statement carries with it a certain air of definitiveness as if the question has been asked and answered (or almost exhaustively answered).

No - it does not


The reality is that we are so far away from even beginning to scratch the surface of making a dent in the "evidence" that would be required to answer the question.

I agree.


It is akin to looking at a newborn adopted infant (without any genetic testing) and stating things like, "there is not one single shred of evidence that this human will ever be able to hold a job", or "there is not one single shred of evidence that this human will become a self-made billionaire". Fine, true statements. But the infant is 7 days old. And when we all die that same infant may only be 11 days old.

Totally false analogy. with nothing to do with the matter at hand.

[Selfsim]

1. There is mounting evidence for ET life sustaining enviroments in the universePlease define why these ETs can be sustained by such environments, without using the term 'Earth-like'.

2. there is mounting evidence for ET life.Please define 'ET life'.


the difference between these 2 is not semanticsThe term 'ET' is semantic .. so is 'ET Life'
Regards

[mutleyeng]

the known discoveries of large numbers of exo planets and their variations, the universe holding more stars than thought as the article suggests, increases the evidence for the existance of et life sustaining environments - earth like or non earth like.

define ET whatever way you want.
for the record, i define it as belonging to a diferent tree of life from us.

[Selfsim]

So why has this thread gone on so long?
I suspect because some folk have fallen for word-play (… more opinion, mind you).


E.g. The atmosphere of Mars is now known to contain a small amount of methane. If we trace that methane to its source, we will either find

* the sort of proof you'd like -- living specimens of a Martian species of methanogen (methane-producing organism).OR
* we may find that a non-living process is producing the methane. In that case, the hypothesis that Mars has a population of methanogens will have been falsified.No, it won't.
What if there are non-carbon based life forms on Mars, producing biogenic methane, but it gets consumed by some other unknown process, and the methane originally detected, is from a non-biogenic source ? (Your conlusion would be erroneous)... Or there exist carbon based ones, that produce a, hitherto, unknown form of non-biogenic methane ?

Or if the 'marginally biogenic' methane has been transported from its production area to another zone, by some unknown process ? (Ie: the notorious 'we didn't look in the right place' problem).

My point is, there is a major issue of being unable to distinguish between a null result and a non result … which can lead to an invalid conclusion. This problem also points to a possibly flawed hypothesis*, (because of a lack of definition of what ET is). A random chance discovery is still, nonetheless, entirely possible.
(I might add, for no real reason, human exploration may also help to minimise the possibility of erroneous conclusions, as humans are well suited to the complex task of detection, under such circumstances ..)


It may not be as exciting as stronger evidence (proof). But the point is, if we follow up that weak evidence it will either lead to stronger evidence, or to falsification.As described above, it may also lead to a non-result .. and if we can't distinguish this from a null result, the hypothesis may be flawed.

Regards
* (But at least it has been cited this time .. thanks for doing so :) ).

[Selfsim]

define ET whatever way you want.I'm starting to be of the view that ET needs to be defined at the exact time and place of a random chance discovery. Its definition in advance, is purely hypothetical and by necessity, unsupported by any non-Earth environmental 'evidence'.

for the record, i define it as belonging to a diferent tree of life from us.That particular definition might also satisfy only one particular individual …
Does that form necessary and sufficient grounds for constituting scientific evidence ?

Regards

[mutleyeng]

That particular definition might also satisfy only one particular individual …
Does that form necessary and sufficient grounds for constituting scientific evidence ?

Regards

nope, its just my definition. It is the single most important defining feature of what i am interested in finding. I dont expect others to agree with me.
If life is found on Mars, it is pretty insignificant for me if we cant isolate it as of unique origin. For others they will be happy with that as being ET.
By my definition, you could also find ET on earth, of earth...thats still good enough for me because we have answered the extra terrestrial aspect through probability. I win either way.

[Selfsim]

If life is found on Mars, it is pretty insignificant for me if we cant isolate it as of unique origin. Yes. I think just about everything depends on the nature of any findings. Everything up until that point is pure speculation, with only subjective support for the conjecture. (Which is all fine, provided the subjective nature is not forgotten nor confused with scientific physical reality).
For others they will be happy with that as being ET.Noted that 'happiness', is also subjective (ie: individual reality).

By my definition, you could also find ET on earth, of earth… I think we'd need another term, other than 'ET', eh …? :)
thats still good enough for me because we have answered the extra terrestrial aspect through probability. I win either way.It is highly 'improbable', hence 'implausible' (I really do object to having to use those terms), that such a finding will be made, because of the vast amount of hard scientific evidence presently supporting the theory of a common origin of terrestrial life.

Regards

[mutleyeng]

i dont really know how plausible it is.
they tell me most life on earth lives under the surface, we havnt checked out all that much of it.
plate tectonics may limit really ancient life...i dont know. At least it gives astrobiologists an excuse for field trips to Yellowstone.
Defining ET or Alien dosnt bother me.
You find something - either it satisfys me or it dosnt

[Selfsim]

i dont really know how plausible it is.
they tell me most life on earth lives under the surface, we havnt checked out all that much of it. Good point.
Last time I checked this out, I found this interesting article, (http://phys.org/news/2011-08-wild-world-millions-unseen-species.html) about a study which figured out that 86% of all species on land, and 91% of those in the sea, have yet to be discovered and catalogued.

The most precise prediction so far, comes up with a total of 8.74 million eukaryote species on Earth. (Micro-organisms and viruses are not included in this figure). 2.2 million (~25%) of these, are expected to be marine dwelling.

So far, about 1.25 million species, (14% of the predicted number), have actually been described and catalogued, and another ~700,000 have been described, but not catalogued, (as at the end of 2011).

As far as I know1 however, with only a handful of minor exceptions2, of all of the catalogued species so far, all have nucleic acid based genomes, and align with the standard genetic code3. All known species have the same 3 polymer types, have the same chirality in the DNA/RNA proteins, and work in accordance with either Glycolysis, Citric Acid or Oxidative Phosphorylation metabolic processes. In all known eukaryotes and the majority of prokaryotes, glycolysis is performed in the same ten steps, in the same order, with the same ten enzymes. All use the ATP molecule as transport for chemical energy within cells.

On its own, the 1.25 million number may not sound very convincing, however, when one considers the full range of statistically possible variations just within what we understand to be the 'Standard Earth-Life Genetic Code', it is quite overwhelming that the same commonality exists amongst all known species here on Earth. Whilst other variants may be possible in pure theory4, it would be extremely exceptional to find something radically different from this model, on Earth5.

Once again, there is no evidence to suggest that any variant of this model, would result in viable 'life', anywhere else.

Regards

1. Happy to be corrected on any of this, (if its in error) … base reference source is a summarised version of 'The Phylogenic Tree'. (http://www.talkorigins.org/faqs/comdesc/section1.html)
2. Which are close standard genetic code derivatives, anyway.
3. There are 1.4 x 1070 informationally equivalent genetic codes, and all known life aligns with just one of 'em !
4. They may be theoretically possible, in number (ie: the maths), but whether these other models result in viable lifeforms, is totally unknown.
5. There is much, much more evidence than just the genetics bit mentioned in this post. That's just the beginnings of it, and excludes anatomical, morphological, DNA, molecular and genetic inheritance evidence.

[Colin Robinson]

What if there are non-carbon based life forms on Mars, producing biogenic methane, but it gets consumed by some other unknown process, and the methane originally detected, is from a non-biogenic source ? (Your conlusion would be erroneous)... Or there exist carbon based ones, that produce a, hitherto, unknown form of non-biogenic methane ? Or if the 'marginally biogenic' methane has been transported from its production area to another zone, by some unknown process ? (Ie: the notorious 'we didn't look in the right place' problem).

Yes, you are right. My statement about falsification was too simple.

Try this one: The hypothesis that measurable amounts of methane in the Martian atmosphere are being produced by a population of methanogenic organisms (Hypothesis A) will be falsified, if and when a non-living process that produces methane is found on Mars, and if the scale of the non-biological methane production is consistent with the measured level of Martian atmospheric methane.

If Hypothesis A does get falsified, there might (as you've pointed out) still be methanogens on Mars that do not produce measurable amounts of methane (Hypothesis B).

One difference between Hypothesis A and Hypothesis B, is that Hypothesis A can be tested, although doing so will take a lot of work. But how would you test Hypothesis B?

As I'm sure you know, the scientific community is more interested in hypotheses it can test, than in those that it can't...


This problem also points to a possibly flawed hypothesis*, (because of a lack of definition of what ET is).

Etymologically, I think you'll find "extraterrestrial" means "beyond Earth". Thus "extraterrestrial life" means "life beyond Earth". However, I don't think anyone would call the residents of the International Space Station "extraterrestrials", even though they are living beyond Earth right now.

I've seen "extraterrestrial" defined as life which originated beyond Earth. If we are going to define it like that, then logically we should define "terrestrial" life as life which originated here. The trouble with definitions like that, is how do you prove a particular family of organisms originated on one planet rather than another? If "terrestrial" and "extraterrestrial" are defined in terms of origin, it would be difficult to prove that "terrestrial" life exists! To do so, you would need to rule out the possibility that the organisms on Earth have descended from an extraterrestrial ancestor.

So it probably makes more sense to define "terrestrial" and "extraterrestrial" not in terms of where the first ancestors of an organism appeared, but in terms of its more recent ancestry...

E.g. If a living organism is found on Mars and turns out to be adapted to Martian conditions to an extent consistent with millions or billions of years of evolution there, then in my opinion it should count as a Martian organism, and as an extraterrestrial one...

In any case, finding such a thing, when and if it happens, will be a breakthrough.

[Colin Robinson]

I think that the wording semantics flow in both directions in this admittedly "open question".

Many often repeat the refrain, "There is still not one single shred of evidence of life outside of Earth" (or something close to that).

This statement carries with it a certain air of definitiveness as if the question has been asked and answered (or almost exhaustively answered). The reality is that we are so far away from even beginning to scratch the surface of making a dent in the "evidence" that would be required to answer the question.

It is akin to looking at a newborn adopted infant (without any genetic testing) and stating things like, "there is not one single shred of evidence that this human will ever be able to hold a job", or "there is not one single shred of evidence that this human will become a self-made billionaire". Fine, true statements. But the infant is 7 days old. And when we all die that same infant may only be 11 days old.

Yes. Our understanding of the universe, and of the distribution of life within it, is like a 7-day-old child.

How it will develop, we don't know.

Science, like baby-care, requires patience.

[Colin Robinson]

the known discoveries of large numbers of exo planets and their variations, the universe holding more stars than thought as the article suggests, increases the evidence for the existance of et life sustaining environments - earth like or non earth like.

define ET whatever way you want.
for the record, i define it as belonging to a diferent tree of life from us.

Some time ago, I listened to a recorded lecture about Titan, by the NASA planetary scientist Chris McKay. IIRC, he defined the word "alien" in the same way you've defined ET. That is, a life-form found here on Earth would qualify as "alien", if it came from a different tree of life. On the other hand, a life-form found on another planet would not qualify as "alien", if it came from the same tree of life.

[mutleyeng]

thanks for post 738 selfism.
It was interesting and certainly puts things into context well.
What would be interesting addition to the data would be to establish reasonable hypothesis as to how you could explain the existance of two surviving trees of life, where one is abundant and the other limited to very small geological/geographical areas. Then run the numbers again for just those the hypothesised environments*.
Basically that limits it to extremophiles and microbial life.


when i say hypothesised environments, the environments are real enough, the hypothetical is that they could hide undiscovered tree of life.

[Selfsim]

But how would you test Hypothesis B? {Insertion by Selfsim: Hypothesis B is: methanogens on Mars that do not produce measurable amounts of methane}...

As I'm sure you know, the scientific community is more interested in hypotheses it can test, than in those that it can't...The smart people at NASA/JPL have already trodden this path years ago ..
So, straight from the horse's mouth (http://msl-scicorner.jpl.nasa.gov/ScienceGoals/) (NASA/JPL's site) …
The MSL mission has four primary science objectives to meet the overall habitability assessment goal:

1) The first is to assess the biological potential of at least one target environment by determining the nature and inventory of organic carbon compounds, searching for the chemical building blocks of life, and identifying features that may record the actions of biologically relevant processes.

2) The second objective is to characterize the geology of the landing region at all appropriate spatial scales by investigating the chemical, isotopic, and mineralogical composition of surface and near-surface materials, and interpreting the processes that have formed rocks and soils.

3) The third objective is to investigate planetary processes of relevance to past habitability (including the role of water) by assessing the long timescale atmospheric evolution and determining the present state, distribution, and cycling of water and carbon dioxide.

4) The fourth objective is to characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary neutrons.
From this it is clear that it has been determined that measurements of the characteristics of the environment surrounding any discoveries, have to be taken, in order to interpret that discovery (especially if we can't specifically characterise what it is we're looking for in advance). This is also what I mean about gathering direct evidence for that database which aims at correlating environmental conditions with anything 'suspect' (meaning 'life' of some sort). The discovery could potentially be meaningless without the habitat data.

Regards

[Selfsim]

and then .. more detail ..


MSL will investigate a site that shows clear evidence for ancient aqueous processes based on orbital data and undertake the search for past and present habitable environments. Assessment of present habitability requires an evaluation of the characteristics of the environment and the processes that influence it from microscopic to regional scales and a comparison of those characteristics with what is known about the capacity of life, as we know it, to exist in such environments. Determination of past habitability has the added requirement of inferring environments and processes in the past from observation in the present. Such assessments require the integration of a wide variety of chemical, physical, and geological observations.

MSL is not a life detection mission and is not designed to detect extant vital processes that would betray present-day microbial metabolism. Nor does it have the ability to image microorganisms or their fossil equivalents. MSL does have, however, the capability to detect complex organic molecules in rocks and soils.

If present, these might be of biological origin, but could also reflect the influx of carbonaceous meteorites. More indirectly, MSL will have the analytical capability to probe other less unique biosignatures, specifically, the isotopic composition of inorganic and organic carbon in rocks and soils, particular elemental and mineralogical concentrations and abundances, and the attributes of unusual rock textures. The main challenge in establishment of a biosignature is finding patterns, either chemical or textural, that are not easily explained by physical processes.

MSL will also be able to evaluate the concentration and isotopic composition of potentially biogenic atmospheric gases such as methane, which has recently been detected in the modern atmosphere. But compared to the current and past missions that have all been targeted to find evidence for past or present water, the task of searching for habitable environments is significantly more challenging (e.g., Grotzinger, Nature Geoscience, 2009).

Primarily, this is because the degree to which organic carbon would be preserved on the Martian surface–even if it were produced in abundance–is unknown. So, my big point in all this is that IF one commences the search NOT from a biased assumption of 'life exists' ... but from a the cold, hard reality of the known facts .. ie: THERE IS NOTHING AT ALL KNOWN ABOUT 'ET LIFE', the test design will end up being scoped, so as to maximise the chances of finding the UNKNOWN. This is such an important point, I can't emphasise it enough !! This was the lesson learned from the Viking Lander ! All the speculation in the world amounts to zip, if one starts to believe any of it ! Exploring demands as unbiased approach as is humanly possible. The only way to achieve this, is by staying focused on physical reality. Forget all this 'opinion' stuff .. all it does is bog down progress ! (That's one huge opinion, I might add, .. but at least I can back it up !) :)

MSL's job is to snoop out as much as it can .. and just maybe, it might find something which catches the watchful eyes of the human minds pouring through the data. The only better alternative to this I can think of, (along with the extra risks and costs), is to actually send 'fully armed', (technologically), humans to snoop it out directly !


Regards

[Selfsim]

The major paper, (book actually), authored by the 'Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council' is called: "The Limits of Organic Life in Planetary Systems; The National Academies Press, 2007".

Its purpose was primarily to provide guidance for NASA on the search for exo-life. The table of contents is here. (http://www.nap.edu/openbook.php?record_id=11919&page=R13)

Of particular interest is the Chapter on "Strategies to Mitigate Anthropocentricity". (http://www.nap.edu/openbook.php?record_id=11919&page=9#p2001293c9970009001)

Here's a quote from that Chapter:


Finally, the committee considered more exotic solutions to problems that must be solved to create the emergent properties that we agree characterize life. It considered a hierarchy of “weirdness”:

- Is the linear dimensionality of biological molecules essential? Or can a monomer collection or two-dimensional molecules support Darwinian evolution?
- Must a standard liquid of some kind serve as the matrix for life? Can a supercritical fluid serve as well? Can life exist in the gas phase? In solid bodies, including ice?
- Must the information content of a living system be held in a polymer? If so, must it be a standard biopolymer? Or can the information to support life be placed in a mineral form or in a matrix that is not molecularly related to Darwinian processes?
- Are Darwinian processes and their inherent struggle to the death essential for living systems? Can altruistic processes that do not require death and extinctions and their associated molecular structures support the development of complex life?
After a hundred pages or so, and eight Chapters, the final conclusions/recommendations are here. (http://www.nap.edu/openbook.php?record_id=11919&page=84#p2001293c9970084001)

The MSL/Curiosity Rover technologies, are a direct flow-on from these recommendations.

This is a great example of how local exploration and the technologies being built into robotic probes aligns with a sound, well though out strategy, which, after much review of what IS known, ends up concluding basically that 'We don't know what's out there.' ... no word-play, no biased beliefs about the presence or absence of exo-life, no vested interests other than pure exploration out of nothing more than: 'Curiosity' !

Speculation ??? Nahh .. forget it .. leave that for Sci-fi movies .. keep it well and truly clear of real Science by swamping it with real, physical, well considered evidence, brought to bear, courtesy of the scientific process, I say.
(Yep .. yet another big opinion .. must be time for me to stop posting ! :) )

Regards

[Colin Robinson]

The smart people at NASA/JPL have already trodden this path years ago ..
So, straight from the horse's mouth (http://msl-scicorner.jpl.nasa.gov/ScienceGoals/) (NASA/JPL's site) …

Well I agree that NASA has some smart people working on these questions.

Actually, you know, the very title of this thread "Evidence for ET is mounting daily, but not proven", is based on a public statement by one of the top smart people -- Carl Pilcher, the current director of NASA's Astrobiology Institute. Here is what Pilcher said


The evidence is just getting stronger and stronger... I think anybody looking at this evidence is going to say, 'There's got to be life out there.'

The opening post of this thread has a link to the article where this quote appears.

[djellison]

"There's got to be life out there"

does not equal

"There is life out there"

[Selfsim]

Well I agree that NASA has some smart people working on these questions.

Actually, you know, the very title of this thread "Evidence for ET is mounting daily, but not proven", is based on a public statement by one of the top smart people -- Carl Pilcher, the current director of NASA's Astrobiology Institute. Here is what Pilcher said

The opening post of this thread has a link to the article where this quote appears.Well the 'top' people are not always the most scientifically literate .. nor are they always speaking the same language as those they might represent .. they are employed as spokespeople to mould and manipulate public opinion .. they are not there to act as scientists.

Look at the OPERA debacle for instance and Ereditato's story (and ultimate fate).

I have mentioned my issues with the field of Astrobiology:

For some strange reason, the field of Astrobiology stands alone in science as having the sole purpose of justifying the belief that its subject matter exists !I am yet to find evidence that preconceived belief isn't the prime motivator for most of what what they say.

Pitcher would seem to be attempting to make serious in-roads by working on public perceptions, (concensus reality), rather than science (physical reality).

I really wish that the public could develop more of a sense of the distinctions between the two, so as to be able to recognise the two distinct motivations behind such messages.
:)
Cheers

[mutleyeng]

well, as a member of the public, i found Pilchers quote in the article to be overzealous, particularly in relation to the arsenic eating microbe, which dosnt seem to have gone down too well outside of NASA.
I think it is unfair to OPERA to compare

The quote from Chris McKay in the same article read like a much more realistic (responcible) thing to say.

I am of course assuming that Pilcher wasnt quote mined

[djellison]

which dosnt seem to have gone down too well outside of NASA.

It didn't go down too well inside NASA either.


Again - I'll put this challenge out there for everyone. If evidence for ET life is mounting....show me a single piece of it.