Evidence for ET is mounting daily, but not proven.

[Jeff Root]

My expectation has always been that life is pretty widespread
in the Universe, and that intelligent life is not uncommon, so
something like finding that arsenic can replace phosphorus in
the DNA of some bacteria isn't much more than "Well, duh!"
for me. It's the sort of thing I'd expect. When I took biology
in high school I wrote a paper on non-carbon based alien life.
That was in early 1969. My paper wasn't very good, but I tried
to discuss some of the possibilities. From what I've learned
since, I have to agree that carbon-based life seems far more
likely, and is therefore probably more common.

A friend created her own major in college. She got her degree
in exobiology. I'll have to ask her to be sure, but I think that
was in the early 1970's.

-- Jeff, in Minneapolis

[A.DIM]

Here? "Mainstream" is pretty much limited to "we haven't found ET yet, but here's some cool ways we're looking."

Yes, that's largely what this thread is about: recent discoveries support the idea ET life could exist, but it's not proven.

The intent of LiS, as I understand its charter, is to discuss the ways we're searching for ET, mostly by trying to locate environments (both actual and hypothetical) that might be habitable, perhaps only by some extremiphile, with perhaps a little (clearly marked) fanBAUTer speculation to tide us over between missions.

Heh, "living critters anywhere but Earth ..."

Well said.

Was it?
Luckmeister's statements seem contradictory to me.
He says, "As to the OP title statement -- there is no mounting evidence for ET. There are however recent findings that Earth life is more tenacious than previously thought, which allows us to "speculate" that chances of survival of life elsewhere, once it has begun, may be higher than we previously assumed."

So ... "recent findings" (eg. extremophiles; potentially habitable Mars, Titan, Europa; feasible alternate chemistries; exponentially increased numbers of stars and potentially habitable bodies around them; etc.) would not be considered "mounting evidence" which make it seem more likely life exists elsewhere?

I don't see the difference.
It almost strikes me as double speak.

[ravens_cry]

What we have is that life here on Earth can exist in ways and places we thought not possible before. We have also found places elsewhere in the solar system that are similar to places we find life on Earth. But I wouldn't call this evidence. Certainly worth looking into and investigating, but not evidence.

[transreality]

If I have an 'idea' for an alien life-form is that 'evidence' for that the existance of that alien life-form?

If not, then why is speculation about possible alien metabolisms evidence for alien life?

Why is evidence for (as we understand them) uninhabitable planets, evidence for life? If not for certain unspoken assumptions, which themselves are as yet unsupported by real observations...

I mean, really, considering Titan to be potentially inhabitable, that is quite speculative considering we are talking a very hostile environment...

[ravens_cry]

I would consider the Viking lander findings to be closer to actual evidence personally.

[Moose]

So ... "recent findings" (eg. extremophiles; potentially habitable Mars, Titan, Europa; feasible alternate chemistries; exponentially increased numbers of stars and potentially habitable bodies around them; etc.) would not be considered "mounting evidence" which make it seem more likely life exists elsewhere?

That's right.

There's a mighty big difference between "evidence of environments that might successfully support life, were it there" and "evidence for ET". Only evidence for the former is mounting. We've yet to find any evidence of the latter, other than extrapolating likelihood from our own existence.

[R.A.F.]

Really, that's what you wanted to leave with, RAF?

You are correct...I find I'm not done here, although it has nothing to do with you...

Perhaps we're all missing the obvious. Perhaps the presence of a large (relative to the parent planet) natural satellite (or moon) is a requirement for a technologically advanced civilization. Just how "rare" are these satellites? Perhaps the universe is crowded with water planets which have no "moons" to "slosh" the water onto the land eventually creating a land based technologically advanced civilization.

STIV not withstanding, we could be surrounded by planets inhabited by super intelligent dolphins, yet never be able to communicate with them. No land based life, no technologically advanced civilization.

Speculation is a 2 edged "sword". We should not only be prepared to speculate about the idea of life elsewhere, we should also be prepared to speculate about the absence of life elsewhere.

[A.DIM]

That's right.

There's a mighty big difference between "evidence of environments that might successfully support life, were it there" and "evidence for ET". Only evidence for the former is mounting. We've yet to find any evidence of the latter, other than extrapolating likelihood from our own existence.

Indeed, one example tells us little, but a distinction to be made then is that there is direct evidence and there is circumstantial evidence; the latter of course, is all we have to work with.

So let me restate my view: circumstantial evidence mounts for ET life existing elsewhere but is not proven.

I doubt though, that had the headline been stated as such we'd have nothing to argue about.

[Luckmeister]

Luckmeister's statements seem contradictory to me.
He says, "As to the OP title statement -- there is no mounting evidence for ET. There are however recent findings that Earth life is more tenacious than previously thought, which allows us to "speculate" that chances of survival of life elsewhere, once it has begun, may be higher than we previously assumed."

So ... "recent findings" (eg. extremophiles; potentially habitable Mars, Titan, Europa; feasible alternate chemistries; exponentially increased numbers of stars and potentially habitable bodies around them; etc.) would not be considered "mounting evidence" which make it seem more likely life exists elsewhere?

I don't see the difference.
It almost strikes me as double speak.

There's a mighty big difference between "evidence of environments that might successfully support life, were it there" and "evidence for ET". Only evidence for the former is mounting. We've yet to find any evidence of the latter, other than extrapolating likelihood from our own existence.

A.DIM Moose's comment is the point I was trying to make. I don't feel it's contradictory.

[Paul Beardsley]

I agree that Luckmeister's point was uncontradictory. Indeed, it was spot-on.

Analogy: We know movie stars like to stay in five star hotels with swimming pools. I've just discovered there's a hotel that meets that description in my home town, so surely that's evidence that there are movie stars in my home town? Hey, I've just learnt that some movie stars like to slum it - they'll stay in five star hotels without swimming pools, and some will even stay in four star hotels! Well, there are quite a lot more of these downmarket places in my home town, so surely the evidence is mounting?

No, none of this is evidence that there are movie stars in my home town. Not even circumstantial.

Similarly, the existence of an environment suitable for life is not in itself evidence for life. Not unless the conditions are themselves dependent on life. So, for example, the discovery of free oxygen in a planet's atmosphere is (circumstantial?) evidence of life on the planet, but the discovery of a planet in its star's goldilocks zone is not evidence of life on the planet.

[ravens_cry]

Wow, thanks Paul Beardsley! I was racking my brain for a good analogy, but that's perfect. Thank you.

[astromark]

I enjoyed that post of 'Luckmeister's'., and find nothing to argue with...

With one foot in my mouth I dare to suggest that although we have no knowledge of it yet.
Life will be found to be thriving where we previously thought it not able to.
That recent science has uncovered this probability is well reasoned.. This subject does require some imagination.
Not the full Monty of science fiction writers., but a more dampened down sub silly fact. Life when found will be 'Different.'
I could be blamed for cranking up that little exchange and It was never intended...
We have only one case study material. Planet Earth. So informed speculative judgment is all we have.

[Paul Beardsley]

Wow, thanks Paul Beardsley! I was racking my brain for a good analogy, but that's perfect. Thank you.

Thanks for the compliment, ravens_cry.

I thought of adding the idea that the presence of a camera crew in my home town might count as circumstantial evidence, but wasn't sure...

[Jeff Root]

The thread title says "Evidence for ET is mounting". That is
exactly correct. It does not say "Evidence of ET is mounting".
That would almost certainly be incorrect. It is remotely
possible that some of the data that has been collected so
far actually does include evidence of ET's, but if so, it is not
apparent.

If you have a five-star hotel in town which has been open
for any length of time, then I'll bet you anything that some
"movie stars" have stayed there. Not being a star, I'll just
stay at the Bear.

-- Jeff, in Minneapolis

[CaptainToonces]

My expectation has always been that life is pretty widespread
in the Universe, and that intelligent life is not uncommon

Really, jeff? But what about the fact that no evidence of it has ever been observed, ever? I mean we can find fossils from a billion years ago, we can find evidence of million-year old asteroid impacts, we can determine the age of the universe, and yet there is no evidence of alien intelligence whatsoever.

Can't we at least say that intelligent life must be very rare?

[Jeff Root]

There is no reason to expect that we would see any evidence of
intelligent ET life even if it is extremely common. Life on Earth
would be very unlikely to be detected by any means we have
used so far, from even the very nearest stars. It would be very
difficult even to detect the existence of the Earth from Alpha
Centauri. We've hardly begun to look.

Intelligent life in our Solar System is evidently pretty rare.
There's no reason to suppose that it is rare in general.

-- Jeff, in Minneapolis

[A.DIM]

What we have is that life here on Earth can exist in ways and places we thought not possible before. We have also found places elsewhere in the solar system that are similar to places we find life on Earth. But I wouldn't call this evidence.
Certainly worth looking into and investigating, but not evidence.

Maybe I'm quibbling, maybe I'm terribly dense, but what else, if not "evidence" might we call these obversations, discoveries and experiments which lend support to the potential for ET life existing in way and places we thought not possible before?

[A.DIM]

If I have an 'idea' for an alien life-form is that 'evidence' for that the existance of that alien life-form?

If not, then why is speculation about possible alien metabolisms evidence for alien life?

Arsenic is directly beneath Phosphorus on the Table; There's good reason to suppose such an alternate chemistry, as many of the same kinds of reactions occur.
I take it you view this discovery merely as "idea and speculation" rather than hypothesis and experiment with positive results?
Let us hear your idea and I'll gladly give you my opinion as to whether or not there's evidence (circumstantial, corroborating, direct).

Why is evidence for (as we understand them) uninhabitable planets, evidence for life? If not for certain unspoken assumptions, which themselves are as yet unsupported by real observations...

I mean, really, considering Titan to be potentially inhabitable, that is quite speculative considering we are talking a very hostile environment...

No doubt.
Here's some recent thinking, though:
Astrobiology and Habitability of Titan;
Biologically Enhanced Energy and Carbon Cycling on Titan.
Couple these with the spaceref "Strategies and Priorities" I linked earlier in this thread and it seems there's good reason to consider Titan habitable.

[A.DIM]

I would consider the Viking lander findings to be closer to actual evidence personally.

Yeah, this coupled with the likes of ALH84001, more recent discoveries on Mars, extremophile discoveries... it sure seems something is mounting, whether or not people want to call it evidence.

[ravens_cry]

Maybe I'm quibbling, maybe I'm terribly dense, but what else, if not "evidence" might we call these obversations, discoveries and experiments which lend support to the potential for ET life existing in way and places we thought not possible before?

I would call it "priorities".
Let's say your looking for your friend Bob. You know Bob likes to be in some places. When first you get to know Bob, the feild of places is fairly narrow, but as you get to know Bob better other places become known, places you never imagined Bob would go. Now a new store opens that shares features with places Bob likes to go, let's say a table top gaming store. If you are looking for Bob and can't contact him, it would certainly be a place to check out, narrow the search a little, maybe, rather then just striking out blindly. But it isn't evidence Bob is there.
All this shows is that Life can exist in various kinds of places, in ways we never imagined. While we look, we should indeed investigate those places first. But I still don't call it evidence.

[A.DIM]

A.DIM Moose's comment is the point I was trying to make. I don't feel it's contradictory.

I don't see how you can think "recent findings" are non evidence when previously it was thought life had no chance surviving in such environments. This thinking was overturned by discovery, observation and experiment. It may be only circumstantial evidence but it has no doubt expanded the potential for ET life existing.

[A.DIM]

The thread title says "Evidence for ET is mounting". That is
exactly correct. It does not say "Evidence of ET is mounting".
That would almost certainly be incorrect. It is remotely
possible that some of the data that has been collected so
far actually does include evidence of ET's, but if so, it is not
apparent.

If you have a five-star hotel in town which has been open
for any length of time, then I'll bet you anything that some
"movie stars" have stayed there. Not being a star, I'll just
stay at the Bear.

-- Jeff, in Minneapolis

Ha!
Well put, Jeff.
I would make that bet too.

[A.DIM]

Really, jeff? But what about the fact that no evidence of it has ever been observed, ever? I mean we can find fossils from a billion years ago, we can find evidence of million-year old asteroid impacts, we can determine the age of the universe, and yet there is no evidence of alien intelligence whatsoever.
Can't we at least say that intelligent life must be very rare?

I'm curious, what evidence would we expect to see if alien intelligence is not uncommon, as Jeff suggested?

[A.DIM]

I would call it "priorities".
Let's say your looking for your friend Bob. You know Bob likes to be in some places. When first you get to know Bob, the feild of places is fairly narrow, but as you get to know Bob better other places become known, places you never imagined Bob would go. Now a new store opens that shares features with places Bob likes to go, let's say a table top gaming store. If you are looking for Bob and can't contact him, it would certainly be a place to check out, narrow the search a little, maybe, rather then just striking out blindly. But it isn't evidence Bob is there.
All this shows is that Life can exist in various kinds of places, in ways we never imagined. While we look, we should indeed investigate those places first. But I still don't call it evidence.

I see.
I would say "getting to know Bob" is equivalent to mounting evidence which suggests he could be found at the new store as well.
It seems a matter of perspective I guess.

"The evidence is just getting stronger and stronger," said Carl Pilcher, director of NASA's Astrobiology Institute, which studies the origins, evolution and possibilities of life in the universe. "I think anybody looking at this evidence is going to say, 'There's got to be life out there."

Sorry Carl, come over to BAUT and you'll find any number of naysayers!

[IsaacKuo]

Can't we at least say that intelligent life must be very rare?

No, because we have barely even scratched the surface when it comes to looking for intelligent life in the universe. We can barely even detect planets outside the Solar System, much less any 21st century-like technological civilizations on them.

So far, the best we can say is that technological life is plausibly rare in the Solar System. But even here in our own back yard, we have barely even scratched the surface. We believe liquid water is a requirement for life, but we have not yet explored a single place with liquid water outside of Earth! Not Europa's ocean, not Encaladus, not Titan, not Ganymede...for all we know, life is common in the Solar System. Europa, Encaladus, and Ganymede also have oxygen, which may be necessary for complex life. So for all we know, there could be technological civilizations almost everywhere there's liquid water.

For now, what we have is an awesome lack of evidence either way.

[ravens_cry]

I see.
I would say "getting to know Bob" is equivalent to mounting evidence which suggests he could be found at the new store as well.
It seems a matter of perspective I guess.

"The evidence is just getting stronger and stronger," said Carl Pilcher, director of NASA's Astrobiology Institute, which studies the origins, evolution and possibilities of life in the universe. "I think anybody looking at this evidence is going to say, 'There's got to be life out there."

Sorry Carl, come over to BAUT and you'll find any number of naysayers!

Until we find another example of life, it doesn't "got to be" anything. I agree SETI is a worthwhile endeavour, I agree looking for Earth like exosolar planets is a good thing, I agree finding and drilling to oceans on Europa and investigating the soil of Mars is fine science and some of our best chances of finding extraterrestrial life.
But it isn't evidence.
To carry the analogy further, let's say you move to a new city and want to make friends like Bob. So you go to places you think people like Bob will hang out. You can't be sure until you do, maybe all the tabletop gamers in this town are into Warhammer 40K and are extroverts and Bob played Dungeons and Dragons and was an introvert.
Evidence would be finding a fossil or a chemical signature that is impossible without life as we know it, or an actual factual specimen.
Possibilities and controversial data aren't, in my opinion.

[baric]

No, none of this is evidence that there are movie stars in my home town. Not even circumstantial.

This is a better panspermia analogy wherein the movie stars represent the life that needs to travel to other towns.

A better analogy would be pool-boys instead of movie stars. Is having a swimming pool a guarantee of having pool-boys? Absolutely not. But would you expect hotels (planets) with swimming pools (favorable environments) to hire (evolve) pool-boys (life)? I think the case is stronger for that.

[Luckmeister]

"The evidence is just getting stronger and stronger," said Carl Pilcher, director of NASA's Astrobiology Institute, which studies the origins, evolution and possibilities of life in the universe. "I think anybody looking at this evidence is going to say, 'There's got to be life out there."

Sorry Carl, come over to BAUT and you'll find any number of naysayers!

I don't like having the term "naysayer" applied in this case. That term implies my disbelief in ET life which is not accurate. I neither believe nor disbelieve it. I'm awaiting evidence rather than possibilities, which is all we have at this point. Possibilities and evidence are not the same thing.

ETA: As to Carl Pilcher calling it evidence -- I would expect that kind of statement from NASA scientists considering their built-in bias concerning ET life. Searching for life is a primary mission funding argument for them. It certainly helps get my support. If I worked for NASA, I would probably develop that bias myself.

[astromark]

Guilty of making assumptions not founded in science, but probability... The science might direct the conclusion but do not confirm it.

Build the robotics. Get them out there.. Looking,. First hand information is required. Nothing else will do.

Unless they visit us. The likely hood of that is diminishing with knowledge... Is that fair ?

I am of coarse just making yet one more assumption. That distance and time prohibit us ever been found... or finding.

Its a interesting turmoil... I so want to know that humanity is not the only sentient race in the galaxy.

That life is actually abundant. At many levels. ... and that I do not want to be food for a invasion force...

I do not know what I want...

[transreality]

Arsenic is directly beneath Phosphorus on the Table; There's good reason to suppose such an alternate chemistry, as many of the same kinds of reactions occur.
I take it you view this discovery merely as "idea and speculation" rather than hypothesis and experiment with positive results?
Let us hear your idea and I'll gladly give you my opinion as to whether or not there's evidence (circumstantial, corroborating, direct).

The evidence is that a particular organism has been found that can metabolise arsenic. The speculation is that the same metabolic pathway could be used by alien life. There are other speculative possibilities too. For example, the most parsimonious explanation would be that the ability has evolved in this species to substitute arsenic for the, as you say, chemically similar phosphorus in an existing metabolic process. A wilder speculation could be that a shadow arsenic-metabolising biosphere exists, has always existed, and predates conventional pathways. Further evidence could distinguish between these speculations. As speculation they are reasonable, but they can't be of themselves be bootstrapped to the status of evidence for still further speculations. That ET has even been invoked in the whole discussion is probably an artifact of the researcher being located in the astrobiology institute more than the research having implications for astrobiology as distinct from say environmental biology.

Couple these with the spaceref "Strategies and Priorities" I linked earlier in this thread and it seems there's good reason to consider Titan habitable

Water looks to be as inert as silicate rock is at terrestrial temperatures; not available to life as a liquid near the surface of titan. The liquids available would be considered deadly solvents to life as we know it. There is little energy from the sun, and lots of cosmic radiation. There are many reasons why Titan may not be habitable, certainly not by life we are familar with.