billions-of-potentially-habitable-planets

[Gomar]

http://www.rawstory.com/rs/2012/03/2...table-planets/


I suppose if that's the case, and any astronomers on those planets could, they probably have found Earth.
Say 10% are capable of sending probes, and they did 1million years ago, then Earth has been studied by
aliens. If any alien probes or beacons or ships are still around Earth, they have either made contact in the
past, or are waiting to do so. Perhaps, they wont at all as they are programmed not to interfere.
However, if that's the case, there must indeed be millions, if not billions, of planets with life in space.
As humans then, or intelligent life of any form, is nothing special nor rare.
Anything humans do, wars, bio/chem weapons, nukes, disease, eco/bio destruction, colonization of the Moon
or Mars, is not of any concern of aliens in the galaxy.

http://www.openminds.tv/planetary-ti...lien-life-870/

[Rhaedas]

Maybe they're on the way.

Maybe their surveys looked for something different than Earth, so we got excluded.

Maybe they came by, but millions of years ago, and didn't see anything worth stopping for.

Or maybe we'll be the first to go looking.

Lots of maybes. All assuming a civilization could get past the fact of huge distances between the stars. Right now the only thing we know is that it would take millions of years to get anywhere, and that's just one destination, one way.

I think the chances of life out there is very good, and intelligent life likely. But for now I can't see how each occurrence will get far from their own system.

[Jeff Root]

I've expressed my views in this sort of thread before. I don't make
any effort to keep those views consistent.

I pretty much agree with Rhaedas. I think there must be lots of life
around the galaxy, including a fair amount of intelligent life. And I
have no doubt that some of that intelligent life has travelled from
their home star systems to others, and more have sent probes to
return data. But I think it is *relatively* unlikely that anyone has
sent a probe to any particular star system, thus relatively unlikely
that any probe has ever reached Earth. Certainly unlikely that any
probe has reached Earth "recently". Meaning, oh, say, the last ten
million years.

I think it is *extremely* unlikely that anyone else has discovered
our (humanity's) existence yet. There may be others who are
close enough, and I have no doubt that there are many who
would be interested if they knew we were here, but I think it is
extremely unlikely that there is anyone close enough who has
the technical capability to discover us who would keep watching
Earth for long enough to have already detected our emergence.

Communication between widely-separated star systems appears
to be difficult and expensive. Travel between them fabulously so,
in addition to being prone to catastrophic failure and having no
commercial value.

That is not to say interstellar travel has no value! It would have
great scientific, cultural, and esthetic value. It just can't have
any *commercial* value because of the long trip times and very
high costs.

-- Jeff, in Minneapolis

[swampyankee]

Probably Edward M Lerner, with his InterstellarNet series has the most likely contact scenario. Trade in anything other than bits is very unlikely.

[Ara Pacis]

... having no
commercial value.

Have you no idea how much people would pay to go to another star system. Not to mention the movie rights. There could be a reality TV show on the interstellar space ship. Not to mention how many spin offs we might get from a new Apollo-like effort. And then when someone comes back, there'd be trinkets to sell and more movie rights and new sit-coms to air about a human and an alien that just happen to get stuck living or working together. It's be a bonanza!

[Jeff Root]

No good, I know it's April Fool's Day!

-- Jeff, in Minneapolis

[kzb]

The billions of habitable planets number comes from extrapolating the HARPS data. They estimate that 41% (range 28-95%) of M-stars have a 1-10 Earth-mass planet in the liquid water range.

However only the other week we had someone extrapolating Kepler data to come up with an estimate of only 0.7% of stars host an Earth-like planet.

I don't think the occurrence of planets or Earth-like planets was ever much of a doubt to people studying this area -it was just assumed that our solar system would be typical, and so Earths should be common. It was other factors in the Drake equation that were more mysterious.

Anyway, although there are serious doubts in my mind about all this statistical data extrapolation, and even whether the methods are actually reliable, eventually these studies should at last give a serious estimate about this factor of the equation. But at the end of it all we'll still be asking "where is everyone ?"

[mutleyeng]

im with Paul Davies on this issue. Untill you have data for a probability of the genesis of life, it is all just idle speculation.
To start answering that, going to Mars is important(but even if it was there, it might be our cousin), searching for second life genesis on earth is important, study of earth rock from the late heavy bombardment is important (maybe on the moon?).

[kzb]

im with Paul Davies on this issue. Untill you have data for a probability of the genesis of life, it is all just idle speculation.
To start answering that, going to Mars is important(but even if it was there, it might be our cousin), searching for second life genesis on earth is important, study of earth rock from the late heavy bombardment is important (maybe on the moon?).

Well, if these habitable exoplanets can be studied in more detail, eventually it will become pretty obvious how common (or not) life is. This will be on planets that supposedly could have temperatures in the liquid water range. I doubt the question will be settled unambiguously in our lifetimes though.

The trouble with Mars life, and second-life genesis on Earth, is how can you be really sure if the life is truly independent? There have been at least two episodes connected with this so far: the fossils in the martian meteorite, and the arsenic-containing bacteria. Need I say more?

[mutleyeng]

well i know next to nothing about biology, but in the case of the metorite, i think i recall it being said that it would be imposible to have been life because of its size. So if it had turned out to be life, thats the kind of thing that would have flagged that it was likely not related.
If you can give them living life there is a lot more they can do...like i say, im not strong on biology but there is all that left/right handed stuff that can give very good indications-this is why we have a whole new field of astrobiology these days

[kzb]

^ I'm simply saying that at least two factors in the equation can be changed from "idle speculation" into hard numbers, by these studies. These factors are, the frequency of habitable planets and (eventually) the occurrence of life on said planets.

It's only the first factor that Kepler and HARPS are providing information on. Hopefully though, having identified potentially Earth-like planets, the race will be on to come up with measurements on atmospheric composition etc on these planets, and thereby come up with clues on life occurrence.

[kzb]

Over on the Centauri Dreams site, there is an article about another very old star apparently hosting planets. It is estimated to be 12.8 billion years old, and has an iron content only 1% that of the sun. It is a "population II" star.

Nevertheless it has two giant planets. If planetary systems formed this early in the history of the Galaxy, it really does highlight the Fermi question.


Planets Around an Ancient Star

http://www.centauri-dreams.org/?p=22397

http://www.idw-online.de/en/attachmentdata15909.pdf

[mutleyeng]

the fermi question is valid IMO,
but really the definition we are using for intelligent life is dictated by what it would require for us to be able to detect them the easy way. ie, being high technology civilisations.
For me, it dosnt matter a jot whether any life out there is intelligent or dumb. And if we do have ways of detecting life other than of advanced technological civilisations, then fermi is no longer problematic because we can redfine what we consider intelligent.

[Jeff Root]

For me, it dosnt matter a jot whether any life out
there is intelligent or dumb.

That matters a lot to me. Intelligent life will talk
with us and tell us about all the worlds they know,
and all the ideas they know. Non-intelligent life
will just sit there and tell us nothing. Since it is
so far away, we will never know anything at all
about it except, possibly, that it exists, based on
observation of light reflected by the planet.

-- Jeff, in Minneapolis

[mutleyeng]

well, you are a lot more optimistic than i am about life in the first place Jeff.
I'll take any life i can get and be thrilled with that.
The prospect of finding an earth like planet just the right distance from its star, which shows tantalising signs of biology....thats more than i have any right to hope for, so id settle for that.

[filrabat]

Probably Edward M Lerner, with his InterstellarNet series has the most likely contact scenario. Trade in anything other than bits is very unlikely.

That pretty much sums it all up. If another species out there is advanced enough to have an InterstellarNet, then it's highly likely it has a DNA (or equivalent) library of thousands of its native species. There's the problem of signal degradation though. So I guess we can "travel" to these planets the same way in which we can "travel" to the Andes when watching TV or YouTube. In principle, we can certainly trade scientific information* of various sorts

*If our species have different environmental requirements, we can DEFINITELY trade information about our "mundane, 'normal' temperature" chemical reactions. IOW, learn A LOT, and VERY quickly about high temperature and low temperature chemistry - including materials sciences. This lets us trade industrial processes. In fact, it might - just might - lead to a whole system of barter exchange (it'd have to be, as money would be useless or impractical in interstellar info exchanges).

Have you no idea how much people would pay to go to another star system. Not to mention the movie rights. There could be a reality TV show on the interstellar space ship. Not to mention how many spin offs we might get from a new Apollo-like effort. And then when someone comes back, there'd be trinkets to sell and more movie rights and new sit-coms to air about a human and an alien that just happen to get stuck living or working together. It's be a bonanza!

Oh God, Ara. Why did you have to bring THAT up <severely grimmacing face>

[KABOOM]

Over on the Centauri Dreams site, there is an article about another very old star apparently hosting planets. It is estimated to be 12.8 billion years old, and has an iron content only 1% that of the sun. It is a "population II" star.

Nevertheless it has two giant planets. If planetary systems formed this early in the history of the Galaxy, it really does highlight the Fermi question.


Planets Around an Ancient Star

http://www.centauri-dreams.org/?p=22397

http://www.idw-online.de/en/attachmentdata15909.pdf

I've read about that "old" star/planet system. It doesn't change much at all for me. Since Hyrdrogen and Helium were essentially the only elements early on it would seem that early stars would have an exceedingly low metal contents and thus any leftover hyrdrogen/helium that didn't get bound into the star would essentially be only able to form "gas giant" planets (which would also lack metals) as its been said that big gas giant planets would have become small stars if they had been even bigger (and thus this would have resulted in a binary star system). Thus, really old gas giant planets should be expected.

[Ara Pacis]

Hmm, can terrestrial-type bodies form around low metallicity stars (and possibly their gas giants) by means of passing through a nebula of appropriate material?

[Selfsim]

For me, it dosnt matter a jot whether any life out there is intelligent or dumb.

And, if the scientific approach is taken, it shouldn't matter 'a jot' whether there is any life out there or not, either !
To be clear, everything else is speculation.

Hopefully though, having identified potentially Earth-like planets, the race will be on to come up with measurements on atmospheric composition etc on these planets, and thereby come up with clues on life occurrence.

Such would be close, in possibility, to a random chance discovery, as inferences drawn from exo-atmospheric composition, about the presence or absence of life, simply leads to more speculation.

I assert that remote exo-atmospheric gas detection methodologies, (over light year distances), as a way of drawing inferences about exo-life, is a fundamentally flawed strategy. The only way I can see, to substantiate the models underpinning them, is by acquiring knowledge from a local discovery of exo-life, or via direct ET contact. Such a discovery, has nothing to do with remote exo-gas/life inference modelling. In the case of unintelligent life, such discoveries can only be caused by the act of direct local exploration, and the evidence gathered from such.

Positing that: (i) exo-life exists and then; (ii) it produces the same metabolic by-products as Earth based life does, is only a way of exploring a speculative premise. This premise seems to give no weight to: (i) the evidence of exo-environmental diversity, (ii) the DNA permutation diversity space and, (iii) evidence of the effects of natural, unrelated, 'stacked' causality factors, which drive the evolutionary process.

It seems to be a strategy primarily aimed at driving ‘hype’ about exo-planet ‘habitability’, rather than leading to rational science.

Regards

[mutleyeng]

thats a bit of a bleak view.
you may be right, as you say everything is speculation -
As a lay person, i try to apply critical thinking as best i can to what i believe to be true. There are plenty of things i would like to be true but do not have any grounds to believe they are.
Yes, i can see you are right, but heres the thing.
If we find an earth like planet just the right distance from its star, and we were able to build a new generation of space craft to carry out atmospheric analysis(is this unreasonable assumption?)- and they tell me they have strong indications of high oxygen, ozone, methane, water, co2 - and the temerature was a nice cosy 15c- yes, i would be wrong to go from my current agnostic position to a believer...but im pretty sure i would.
The science would be perfectly rational, but it would be fair for you to argue that i wasnt....maybe. To argue that on scientific grounds wouldnt you have to be able to demonstrate how those indicators could come about without biology?
It would then be up to you to try to dispell the hype that would surely follow, good luck with that.
I also think you are right we are making assumptions about the nature of life being as we know it, but what else can we do?
How could we possibly look for life that we have no knowledge of the enviroment and mechanisms that life requires...short of waiting for ET to call, i cant see what else we could do.

[Selfsim]

Hi Mutleyang;
Thanks for your reply .. I'm not having a go at you, or your beliefs here (apologies if it seemed that way) .. but I do find the thinking quite fascinating ..

If we find an earth like planet just the right distance from its star, and we were able to build a new generation of space craft to carry out atmospheric analysis(is this unreasonable assumption?)- and they tell me they have strong indications of high oxygen, ozone, methane, water, co2 - and the temerature was a nice cosy 15c- yes, i would be wrong to go from my current agnostic position to a believer...but im pretty sure i would.
The science would be perfectly rational, but it would be fair for you to argue that i wasnt. It would then be up to you to try to dispell the hype that would surely follow, good luck with that.

... so help me to understand this ...
If all these things were to come together, (about one particular exo-planet), then you'd definitely believe that it harbours life, (presumably identical to our own) ?
And this belief would be satisfying, in spite of it not being feasible to confirm it, (by direct testing) ? This belief would then become reality for you.

So, the journey to the resulting hype, is more satisfying and conclusive for you, than embarking on some other journey where there exists an assured outcome, and finality ?

Once again .. I'm not out to criticise anything here .. I just find the whole concept, (and worldview), radically different to my own .. and thus, kinda interesting !

Regards

[mutleyeng]

no worries, its a conversation, i didnt feel you were attacking me at all.

If all those conditions came together, in my mind i would go from being neutral about exo planet life to having a very high confidence that it existed. Just how high would depend on whether there were actually any known non biological mechanisms that could explain it. If there were not any of merit, my confidence would be extremely high untill such time as new evidence may question it.
I would not necessarily presume it was simular to our own other than following our understanding of biology...maybe it is rna not dna, but yes i would have to assume it uses simular mechanisms.
would that be good enough for me? yes, it would make my day big time.
the rest of your questions seem to be contingent on my lifetime. I dont care if we are on a journey that will not give finality in my own lifetime...the journey will be ongoing over many generations, and im good with that. I want answers, and i want to know things i currently dont, but i also think we need the stimulation of questions that are very difficult to answer.

[kzb]

Selfsim,
you are correct in many ways of course, in particular, it is unlikely that an Earth double will be found. Instead, it will be more likely that various strange combinations of atmospheric chemicals will be discovered and some people will argue that some of them are a sign of life, and others will argue they are no such thing.

But if an Earth-size planet is discovered with an atmosphere similar to Earth's, I think you'd have to be an extreme skeptic to say that is not 99.9% proof of life.

SO what do you suggest instead? Everything is political. There is not going to be a multi-trillion dollar interstellar probe, even in our grandchildrens' lifetime. It's got to go in stages, with the political will generated to move on to the next stage.

[Selfsim]

Hi kzb;
Thanks for your replies .. I should also make it clear that I'm making a genuine attempt to understand (and respect) your viewpoints as well.

Selfsim,
you are correct in many ways of course, in particular, it is unlikely that an Earth double will be found. Instead, it will be more likely that various strange combinations of atmospheric chemicals will be discovered and some people will argue that some of them are a sign of life, and others will argue they are no such thing.

Well, that wasn't really my point. Frankly, I have no idea whether a second Earth might be found or not (and I don't really care whether one is found, or not).

They might find some ! What is consistent so far, with the Kepler discoveries, is the environmental diversity. I'm also not solely focused on the environment factors. This is not the only variable effecting critically balanced causality factors in modern day biological systems, nor their evolution over time. Consideration of these latter aspects, is what leads me to a way less certain outcome, than most posters in this section of BAUT seem to hold 'true'.

But if an Earth-size planet is discovered with an atmosphere similar to Earth's, I think you'd have to be an extreme skeptic to say that is not 99.9% proof of life.

Ok, so here's something I do have an issue with.
I notice you're using a statistic as an attempt to reinforce your point view. The statistic has zero basis in physical or theoretical reality. (If I am mistaken, and indeed it does, then please demonstrate it for us).
I can only conclude that its use is purely political (as per your confirmation of this in your next comment).
I have a problem with using mathematical-sounding language, in order to project a political viewpoint.
Every ounce and millisecond of training and time spent in acquiring mathematics and scientific skills is spent with the goal in mind, of stripping away such biases. To then reintroduce such biases into the discussion, demonstrates to me, a lack of consistency in a clearly scientific discussion, (ie: a lack of integrity, in the 'completeness and wholeness' sense of the word).

SO what do you suggest instead? Everything is political. There is not going to be a multi-trillion dollar interstellar probe, even in our grandchildrens' lifetime. It's got to go in stages, with the political will generated to move on to the next stage.

'Everything' is not political. Science has been created specifically for us to focus on reality .. and to keep our perceptions as free from bias as is possible. Politics is about creating a reality amongst a community of humans (an alternate reality from physical reality). Much of science is counterintuitive, and we wouldn't know that, if we spent all our time in the alternate reality of 'community'.

I take a stand to make it clear that the 'alternate reality' of community, created by bandying about scientific (or mathematical) terminologies and concepts, is yet another abuse of science .. so we should at least, be aware of when this is happening in a conversation. The use of science in this way, leads to the creation of pseudo-sciences, and deception.

"Multi-trillion dollar interstellar probes": There is no need for such a thing. The Laws of Physics cannot be circumvented by expending our limited resources. Why would anyone even suggest this is feasible ?

"SO what do you suggest instead?": It is easily argued ('community reality', now ), that local exploration of our Solar System has resulted in scientific and sociological benefits way beyond most human and scientific value measures. In comparison with: 'exo-atmospheric-gas-detection-and-analysis-over-light-year-distances', its returns on investment, can at least be demonstrated to be certain.

Cheers

[Selfsim]

I want answers, and i want to know things i currently dont, but i also think we need the stimulation of questions that are very difficult to answer.

Science is fundamentally about posing questions and pursuing them. The result is almost always more questions. This is where the 'stimulation' you mention, comes from.

Pursuing answers, is the focus of philosophy.
The answers provided by philosophy, are not where the 'stimulation' comes from.
Philosophy is separate from science.

Regards

[mutleyeng]

philosphy, that is modern philosophy, does not provide any answers. Its only purpose (in my world view) so far as science is concerned is to help formulate what questions to ask.
i also have a bit of a problem with this certainty you keep talking of... science never gives you certainty.
so far as the conversation above, where you complain about the use of statistics i absolutley agree with you. i dont think kzb was literally meaning that would be a scientific probabiity mind you.
the problem i get from your case for the study of our solar system for me is, so far as the big question is concerned, it may not actually get us anywhere. Its not finding life that really matters, its finding something we can be sure is a second genesis. It may be you could find life in the solar system that is so different that it is clearly a seperate genesis of life....but theres a pretty good chance it will be inconclussive.
if you find an atmosphere which shows stronge evidence of exo-planet biology, then it is almost certain to be an independent genesis.

[Selfsim]

philosphy, that is modern philosophy, does not provide any answers. Its only purpose (in my world view) so far as science is concerned is to help formulate what questions to ask.

I don't see many problems with posing questions from a philosophical basis. Many of great scientific discoveries started out in exactly this way. I personally find no answers in philosophy, either. Curiously, others do, however.

also have a bit of a problem with this certainty you keep talking of... science never gives you certainty.

Well, I think that was my point. In this particular case, the more and deeper scientific considerations added to the mix, the less certain the outcomes appear to be when it comes to remote exo-gas inference. The 'certainty' I mention, (in the last paragraph of my post #24), actually comes from the risk assessment of two options .. which has more to do with the business of exploration, (a 'community reality'), than with science. (The returns from local exploration are well known, hence more certain).

If I ask: 'How can I discover life remotely over light-year distances ?', I will find no certainty, because the answer is model dependent, and that model in turn, either depends on data which is absent until exo-life is discovered, or is dependent on the discovered life to be Earth-like, or by some other 'first contact' means.

Its discovery locally, if it exists, is at least, practically feasible. Because we know of ‘habitable zones’ locally, a null finding still adds to knowledge of 'habitability zone' conditions. (Not to mention the spin-off technological benefits directly attributable to the more complex enterprise).

Its discovery (or verification) over light-year distances, is not feasible in practice .. we already know this .. no verifiable progress towards the definition of 'habitable zone' is achievable, because exo-life cannot practically be confirmed following some instance of exo-atmospheric gas detection.

so far as the conversation above, where you complain about the use of statistics i absolutley agree with you. i dont think kzb was literally meaning that would be a scientific probabiity mind you.

Being somewhat blunt; "then don't quote meaningless, undemonstrable statistics !" (Please note: I mean this metaphorically .. not personally). Understand the tools one is using, before attempting to use them in a scientific sense, in a science forum.

the problem i get from your case for the study of our solar system for me is, so far as the big question is concerned, it may not actually get us anywhere. Its not finding life that really matters, its finding something we can be sure is a second genesis. It may be you could find life in the solar system that is so different that it is clearly a seperate genesis of life....but theres a pretty good chance it will be inconclussive.

There goes that 'chances' word again .. you are presuming an outcome which is undeterminable. The 'chance' is unknown.
The more complex the task, the more intelligence needs to be directly applied to that task. Technologically armed local human examination, is the best method we know for undertaking complex tasks - like exo-life verification.

if you find an atmosphere which shows stronge evidence of exo-planet biology, then it is almost certain to be an independent genesis.

Why ?

Regards

[eburacum45]

If a planet the same 'size' as Earth is discovered with an oxygen/nitrogen atmosphere that might mean several things; a waterworld with a deep ocean could have an oxygenated atmosphere, without any life being present. However such a planet would be somewhat less dense than Earth. The temperature is important too; a planet with a surface temperature of +600K would not support any kind of life I can easily imagine.

If we find a planet that is the same temperature, density and mass as the Earth, and one that is not likely to be tidally locked (as most of those 'billions' of Earth-like planets mentioned in the OP are likely to be) then life would be a very likely explanation for the existence of an oxygen rich atmosphere. Without life our oxygen would probably only last about a million years or so before it is absorbed by the crust.

But exact Earth-clones are likely to be very rare; on the other hand life may be commonplace on planets that do not resemble Earth very much at all.

[mutleyeng]

first, sorry, i dont use forums that often and i never worked out how to multi quote.

most of science knowlege is model dependent.
what have you learnt from a null finding? what "habitable zones" do we know of locally...other than on earth?

Its discovery (or verification) over light-year distances, is not feasible in practice .. we already know this .. no verifiable progress towards the definition of 'habitable zone' is achievable, because exo-life cannot practically be confirmed following some instance of exo-atmospheric gas detection.

can you demonstrate to me that this is true? I appreciate we do not currently have the hardware to do analysis of exo planet atmospheric conditions right now, but my approval of the quest is that the ability to do so is not beyond known technology.

Being somewhat blunt; "then don't quote meaningless, undemonstrable statistics !" (Please note: I mean this metaphorically .. not personally). Understand the tools one is using, before attempting to use them in a scientific sense, in a science forum.

i agree to an extent, but this is a forum about science, not a science forum. most of us are lay persons i would guess (sorry to guess, but hey)

There goes that 'chances' word again .. you are presuming an outcome which is undeterminable. The 'chance' is unknown.

yep, thats the frontiers of science for you. we are making hypothosis here, we can only really weigh chances.

The more complex the task, the more intelligence needs to be directly applied to that task. Technologically armed local human examination, is the best method we know for undertaking complex tasks - like exo-life verification.

Why ?


demonstrate to me that you would be able to distinguish two biological lifes as being two seperate genesis.
if you are talking about completely diferent base life forms, the best way to do that is on earth, forget the solar system. The problem you have with an entirely different base life, is how do you look for it?
(addition added) as to why could analysis of exo planet atmosphere give strong indications of life...its because we have models that require only biology to create those indicators. Yes that could be we doont know enough, but you can apply that logic to any field of science...the standard model might be wrong, but for now we assume it is not, mainstream science at least.

[eburacum45]

...demonstrate to me that you would be able to distinguish two biological lifes as being two seperate genesis.

If I may answer this particular question;
Life on Earth can be demonstrated to have evolved from a primordial common ancestor using phylogenetics. See
http://en.wikipedia.org/wiki/Last_universal_ancestor
Any biota originating from another world would not share a common ancestor with Earth-life, unless there had been some sort of genetic transfer between the worlds.

Interstellar genetic transfer could happen naturally, via panspermia (but the chances of such a event happening can be calculated, and are very low indeed) or by deliberate transfer by a hypothetical advanced civilisation. No one knows how likely that is.