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Thread: billions-of-potentially-habitable-planets

  1. #61
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    Two stars pass within a few AU of each other perhaps monthly somewhere in our galaxy, so advanced beings can transfer between solar systems almost as easily humans can travel to Titan or the big moon of Neptune. Admittedly this likely has not happened to our solar system yet, but at least a few inhabited planets likely started habitation in this way. Neil

  2. #62
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    Quote Originally Posted by swampyankee View Post
    I think trying to search where we think vaguely Earth-like life (carbon based, using water as a solvent, at a temperature between about 273 and 373 K, etc) may exist is the only rational starting point. The logic for this is that we've got a better chance of recognizing this kind of life than a life-form living in the methane/ethane lakes of Titan. I'm not entirely sure that on-the-spot human explorers would recognize alien life before it literally bit them on the nose.
    Titan's lakes differ in composition from Earth's lakes. All the same, they are recognizable as lakes. Alien life may differ in composition from Earth life, but if it has mouths to bite us with, it will be recognizable as life.

  3. #63
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    Quote Originally Posted by Colin Robinson View Post
    Let me give you one example of where "speculation" can lead to.

    The 1952 Miller-Urey experiment, applied an energy source to a hydrogen-rich mixture of gases, dissolved the results in water, and demonstrated formation of compounds including amino acids.

    This classic piece of lab work tested the hypothesis put forward 28 years earlier by Alexander Oparin and J.B.S. Haldane, that life on Earth could have developed from an ancient atmosphere that was hydrogen-rich, rather than oxygen-rich.

    When Oparin and Haldane put forward that hypothesis, they had no way of testing it. They were speculating. And they may have been quite wrong, about the make-up of the atmosphere of ancient Earth.

    But the bottom line is...

    Disciplined speculation can and does stimulate history-making empirical research.
    G'Day Colin;

    I need to answer your question from several posts ago ... when I say 'local', I am thinking primarily of Solar System exploration, but I see no particular reason to exclude lab-based biological research, or extremophile research (on Earth, Earth Orbit, etc), either. Basically, whatever can be shown to result in some tangible incremental contribution to the end goal is what I'm on about.

    Thus, addressing your point above .. sure .. disciplined speculation by scientists living in the real-world, is a tried and tested way of evolving thinking. There are many other examples of this throughout scientific history.

    So what does this have to do with a speculative undertaking which can only lead to inference vs an undertaking which has a chance of producing verifiable evidence of directly correlated data ?

    Regards

  4. #64
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    Quote Originally Posted by Selfsim View Post
    G'Day Colin; I need to answer your question from several posts ago ... when I say 'local', I am thinking primarily of Solar System exploration, but I see no particular reason to exclude lab-based biological research, or extremophile research (on Earth, Earth Orbit, etc), either. Basically, whatever can be shown to result in some tangible incremental contribution to the end goal is what I'm on about.
    Thank you for explaining what you mean by "local".

    Thus, addressing your point above .. sure .. disciplined speculation by scientists living in the real-world, is a tried and tested way of evolving thinking. There are many other examples of this throughout scientific history.

    So what does this have to do with a speculative undertaking which can only lead to inference vs an undertaking which has a chance of producing verifiable evidence of directly correlated data ?
    That depends which speculative undertaking you have in mind. I agree with you that the question of life on extra-solar planets is likely to remain unanswered for a long time. On the other hand, if answers are ever going to be found, I'm inclined to think speculation will be part of the process that gets us to that stage.

    Re local research... when swampyankee mentioned ideas about life based on a solvent other than water,

    Quote Originally Posted by swampyankee View Post
    People are speculating about alternatives to water as a solvent for life, including ammonia, various hydrocarbons, liquid nitrogen, supercritical carbon dioxide, and molten salts. Each will have its own habitable zone, and some of them would probably consider life at liquid water temperatures (which span from about 273 K to about 647 K) as impossible.
    you said

    Quote Originally Posted by Selfsim View Post
    this is exactly what I'm on about when it comes to rampant speculation !
    Yet we know already that within our own solar system there is at least one world with large amounts of one class (at least) of liquid other than water.

    I'm talking the lakes of liquid methane/ethane on Titan, because their existence is established. However, other solvents mentioned by swampyankee may exist within our solar system too. E.g. According to the astrobiologist William Bains subsurface liquid nitrogen is considered possible for Neptune's moon Triton.

    Thus, if life based on liquid methane or liquid nitrogen is considered theoretically possible, surely this says something about what we can look for locally, and where we can look for it?
    Last edited by Colin Robinson; 2012-Apr-08 at 08:49 AM. Reason: small stylistic fix - italics

  5. #65
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    Colin;

    If you object to my usage of the term 'rampant' in describing a particular BAUT behaviour, that's ok .. 'twasn't in reference to the topic of disciplined scientific speculation anyway. My post #63 clarified the more important point, and I agree, that disciplined speculation is a valuable part of science.

    As far as the chemical solvent variants mentioned by swampyankee occurring within our own solar system goes, I'd have to request links to appropriate peer-reviewed papers and studies, (rather than going by heresay), before commenting further. Swampy's words pointed out that these ideas were speculative. At the highest level however, notice how speculation has the effect of diverging the present water-based Habitable Zone search space strategy? Disciplined scientific speculation coming from Astrobiology, I thought, targetted a convergence effect ... interesting. (Perhaps this is just part of the 'early-days-yet' toing and froing phenomenon ?)

    Anyway, if these variants have substance behind them, and demonstrate appropriate rigor and discipline, then I can at least, see that investigating such HZs within our solar system, at least has a chance of being capable of contributing to an interpretive database of evidence which correlates planetary atmospheric compositions with exo-life findings, (or non-findings, as the case may be).

    Regards

  6. #66
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    theres the problem with a concentrated approach when you (science) are at the limits of knowledge.
    Ive heard very learned people say that nitrogen base is impossible.
    If you go to titan and there is no life found, have you learnt that methane cannot be a solvent of life? of course not. you have just learnt that there is no life on titan.
    compare this issue to theoretical physics... should there be a concerted effort on string theory? or is it better to have as many avenues of research as can be accomodated.
    I dont have a problem with selfisms argument as where the best empirical answers would come from, or indeed that the study of our system would likely expand our knowledge of biology regardless.
    what i want to know is, has abiogenesis happened in another star system. I dont expect to have concrete empirical confirmation of that, but i could expect to have very strong indications (if it exists). It may come from biology within our solar system, it may come from exo planet study. Lets have them both please.
    I think its more the concerted effort in one direction that bothers me.

  7. #67
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    Quote Originally Posted by mutleyeng View Post
    I think its more the concerted effort in one direction that bothers me.
    Agreed ... (in an ideal world).

    Perhaps I should revise my assertion to read:

    "Spectroscopically sourced exo-planetary atmospheric gas analysis, used as a method for inferring the presence or absence of exo-life, at light year distances, is a fundamentally flawed strategy unless local exploration also proceeds simultaneously ?"



    Regards

  8. #68
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    I wouldnt have a problem with that. Its always going to be about degrees of confidence. the more data you have from any source, the better the interpretation

  9. #69
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    Quote Originally Posted by Selfsim View Post
    As far as the chemical solvent variants mentioned by swampyankee occurring within our own solar system goes, I'd have to request links to appropriate peer-reviewed papers and studies, (rather than going by heresay), before commenting further.
    Re Neptune's moon Triton, and possibility of life using liquid nitrogen as a solvent, see William Bains in the peer-reviewed journal Astrobiology, Vol 4, page 137 - 167

    I don't think you can read this actual article without paying for the privilege, unless you know a library that has the journal. However, its author, William Bains has also written a less formal article about the same topic, which can be read free online.

    Re Existence of methane/ethane lakes on Titan
    see E.R.Stofan et al "The lakes of Titan" in Nature 445, 61-64 (4 January 2007)

    The abstract states: "Here we provide definitive evidence for the presence of lakes on the surface of Titan".

    Regarding the overall question of life in non-water solvents, see chapter 6 of the report by the US National Research Council subcommittee on The Limits of Organic Life in Planetary Systems


    Swampy's words pointed out that these ideas were speculative. At the highest level however, notice how speculation has the effect of diverging the present water-based Habitable Zone search space strategy? Disciplined scientific speculation coming from Astrobiology, I thought, targetted a convergence effect ... interesting. (Perhaps this is just part of the 'early-days-yet' toing and froing phenomenon ?)
    Yes, if what you mean by "convergence effect" is an effort to narrow the search, I think that has been happening. It's obviously unfeasible to try to look everywhere -- to turn over every rock in the solar system, or even every rock on Mars, for example, to see if anything is crawling about underneath. So some astrobiologists came up with the the idea of following the water -- since all known life has liquid water in its cytoplasm, look for other places in the solar system (or beyond) that may have liquid water now, or may have had it in the past. But other astrobiologists thought that you narrow the search too much if you don't consider the possibility of fluids other than water as solvents for life. It is, as you say, a toing and froing thing...
    Last edited by Colin Robinson; 2012-Apr-09 at 01:48 AM. Reason: Added name of journal

  10. #70
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    Quote Originally Posted by Selfsim View Post
    So I should make it clear that the point being made here pertains only to the making of progress in the exo-life discovery goal. (...)
    If I understand it right, you have problem with interpreting results of exo-atmosphere measurements in light of extraterrestial life, because it is next to impossible to prove that unstable atmospheres/strange properties/whatever it is indeed caused by life, not some exotic non-biological chemistry. Am I right?

  11. #71
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    Quote Originally Posted by MaDeR View Post
    If I understand it right, you have problem with interpreting results of exo-atmosphere measurements in light of extraterrestial life, because it is next to impossible to prove that unstable atmospheres/strange properties/whatever it is indeed caused by life, not some exotic non-biological chemistry. Am I right?
    Ok ... I don't have any 'problems'.

    The issue, on the other hand, is that inanimate matter is distinguished over life, by a lack of very specific functions.
    If these functions are possessed by something, then that 'something', is then classified as living.
    In the case of 'unintelligent life', these functions are unable to be remotely diagnosed.
    They can be locally tested, however.
    Examining reflected light remotely, leads to inference, as a means for determining 'life'.
    Inference and deduction determinations, are based on statistical significance.
    Statistical significance requires information about parent distributions.
    We have no such information in the case of exo-life.

    Localised testing over light-year distances, in order to gather this information, is not feasible.

    Regards

  12. #72
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    Selfsim wrote:
    Localised testing over light-year distances, in order to gather this information, is not feasible.

    I think you give up too easily!

    Like it or not, this is inevitably the next stage. Inevitably there are going to be mass debates over what it all means. And I still think that if a planet is observed to have similar atmosphere and light curves to Earth, that will mean something.

  13. #73
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    I think Selfism has a point, that spectroscopic analysis of the
    atmospheres of distant planets will not be clear and obvious
    in its indications of the presence of life, but essentially I reject
    the gist of it. Lots and lots of things are determined by
    circumstantial evidence. This will just be another. If it looks
    like a duck, and acts like a duck, and sounds like a duck, then
    chances will be pretty good that it is a duck. The more certain
    you want to be about it, the more carefully and completely you
    will examine it. Maybe we will find lots of planets that look and
    sound a lot like they have life, but none that look and sound so
    much like they have life that we can reasonably feel confident
    that they really do have life. So what. We'll worry about that
    situation if and when we run into it.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  14. #74
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    Quote Originally Posted by Jeff Root View Post
    I think Selfism has a point, that spectroscopic analysis of the
    atmospheres of distant planets will not be clear and obvious
    in its indications of the presence of life, but essentially I reject
    the gist of it. Lots and lots of things are determined by
    circumstantial evidence. This will just be another. If it looks
    like a duck, and acts like a duck, and sounds like a duck, then
    chances will be pretty good that it is a duck. The more certain
    you want to be about it, the more carefully and completely you
    will examine it.
    I think you'll find that the real quest driving the whole exo-life enquiry, is the question about a second genesis. Remote spectroscopic analysis (or spectropolarimetry), will also not resolve this deeper question.
    Exploration of the surface will. This is not feasible, if the sample is at light-year distances.

    Quote Originally Posted by Jeff Root
    Maybe we will find lots of planets that look and
    sound a lot like they have life, but none that look and sound so
    much like they have life that we can reasonably feel confident
    that they really do have life. So what. We'll worry about that
    situation if and when we run into it.
    You mean Mars, eh ?

    Bring on Curiosity !

    Regards

  15. #75
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    Quote Originally Posted by kzb View Post
    Quote Originally Posted by Selfsim
    Localised testing over light-year distances, in order to gather this information, is not feasible.
    I think you give up too easily!
    Your opinion is noted and respected, but does not addresss the timeframe from which my statement was framed (ie: in the present).

    The future is just as unknown as whether exo-life exists or not, (ie: the actual subject matter, which my statement is addressing).

    Quote Originally Posted by kzb
    I think you give up too easily!

    Like it or not, this is inevitably the next stage. Inevitably there are going to be mass debates over what it all means. And I still think that if a planet is observed to have similar atmosphere and light curves to Earth, that will mean something.
    Humans are meaning-adding machines !

    I'm sure the meaning we add to such an observation, will also be describable in statistical uncertainty terms. Whether amateurs ever bother to understand what this actually means, is another question.

    This is also where I can see that the tenacity you call for, (ie: 'not giving up too easily'), once applied, might result in a productive conversation. Applying tenacity directly to what is inherently uncertain, (courtesy of nature), on the other hand, leads to dogma.

    Regards

  16. #76
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    Quote Originally Posted by Selfsim View Post

    Examining reflected light remotely, leads to inference, as a means for determining 'life'.

    Regards
    I agree that one shouldn't jump to conclusions from limited evidence, but if life seems to be the only or more likely explanation of a planet's atmospheric composition it makes sense to at least entertain the hypothesis that there's life. If you're saying don't jump to conclusions about life, then I agree, but if you are saying we shouldn't do these remote measurements of planetary atmospheres because it doesn't conclusively prove that there's life, then I strongly disagree. Much can be learned from such observations by correlating atmospheric composition with the conditions in the solar system where the planet is located. We would then have a better idea of the kinds of solar systems where life may possibly exist.

  17. #77
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    It's clear to me that he's saying something in between:
    We should do all the remote observation we can, but it
    will never be good enough to determine whether what
    we observe is due to life.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  18. #78
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    I might as well reply to this as long as I'm here.

    Quote Originally Posted by Selfsim View Post
    Quote Originally Posted by Jeff Root View Post
    I think Selfism has a point, that spectroscopic analysis of the
    atmospheres of distant planets will not be clear and obvious
    in its indications of the presence of life, but essentially I reject
    the gist of it. Lots and lots of things are determined by
    circumstantial evidence. This will just be another. If it looks
    like a duck, and acts like a duck, and sounds like a duck, then
    chances will be pretty good that it is a duck. The more certain
    you want to be about it, the more carefully and completely you
    will examine it.
    I think you'll find that the real quest driving the whole exo-life
    enquiry, is the question about a second genesis.
    I've been interested in the subject for at least fifty years.
    For me, the question of how often life arises has always
    been a subset of the question of where life can be found.
    That also seems to be true for the people I know personally
    who have a degree in astrobiology or who work on SETI.
    The question of how, where, when, how quickly and how
    often life arises is very interesting and very important to
    me, but it isn't what motivates me to be interested more
    generally in discovering and learning about extraterrestrial
    life. If follows from my more general interest.

    Quote Originally Posted by Selfsim View Post
    Remote spectroscopic analysis (or spectropolarimetry),
    will also not resolve this deeper question.
    There is no good reason why it shouldn't. It depends on
    how carefully we look and what shows up when we do.

    Quote Originally Posted by Selfsim View Post
    Exploration of the surface will. This is not feasible, if the
    sample is at light-year distances.
    That's true in the short term and medium term. If there
    is good spectroscopic evidence for life on some relatively
    nearby planets, though, we will eventually visit at least
    some of them to learn more.

    Quote Originally Posted by Selfsim View Post
    Quote Originally Posted by Jeff Root View Post
    Maybe we will find lots of planets that look and sound a
    lot like they have life, but none that look and sound so
    much like they have life that we can reasonably feel
    confident that they really do have life. So what. We'll
    worry about that situation if and when we run into it.
    You mean Mars, eh ?
    You know I didn't.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  19. #79
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    Quote Originally Posted by Paul Wally View Post
    I agree that one shouldn't jump to conclusions from limited evidence, but if life seems to be the only or more likely explanation of a planet's atmospheric composition it makes sense to at least entertain the hypothesis that there's life.
    I question the 'sense' in entertaining such a hypothesis if there can be no definitive resolution by means of verification. If an exo-atmosphere is light years distant, there can be no such resolution.
    To continue with a hypothesis which is neither verifiable nor falsifiable by practical means, seems destined to become an obsession.

    … I gotta call it like I see it (in this particular case) .. apologies for eliminating areas of grey in what I'm saying, but I really do think some folk have lost sight of practicality constraints. No matter how intense one's dream might be, some things simply aren't feasible. Retrieveing verification evidence over light-year distances is one of 'em.

    Quote Originally Posted by Paul Wally
    If you're saying don't jump to conclusions about life, then I agree, but if you are saying we shouldn't do these remote measurements of planetary atmospheres because it doesn't conclusively prove that there's life, then I strongly disagree. Much can be learned from such observations by correlating atmospheric composition with the conditions in the solar system where the planet is located. We would then have a better idea of the kinds of solar systems where life may possibly exist.
    Ok .. so we live in a non-ideal world, where resouces are constrained. If there exists other options/tests/experiments which can be demonstrated to make tangible returns on the sole basis of exo-life exploration, which can be demonstrated to be practically verifiable and falsifiable, I'd have to prefer those alternatives.

    I don't have a problem acknowledging the spin-off benefits (eg: technological etc), derived from pursuing a dream, but these can also be obtained by pursuing more practical options ..

    Regards

  20. #80
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    Quote Originally Posted by Jeff Root View Post
    It's clear to me that he's saying something in between:
    We should do all the remote observation we can, but it
    will never be good enough to determine whether what
    we observe is due to life.
    .. Even if we found remotely, (at present-day telescopic resolution scales), what seemed to be an exact duplicate of Earth, there is still no reason to assume that exo-planet will have our type of life, no life, some variant of it, or had some variant of it, which became non-viable, or left the planet, etc, etc …

    The means for enabling the extrapolation from Earth's case history, is limited by the laws of physics, chemistry, and randomness, at certain scale levels. Whilst these Laws might be ubiquitous throughout the observable universe, and would thus influence the outcome of life emergence (and subsequent evolutionary processes), the outcome(s) of their complex interactions, can render the outcomes completely unpredictable at some scale levels, and we know this specifically because of the known complexity associated with life.

    If we cite Earth-life as our starting point of evidence for life, then we should include the entirety of what we know about it, and Earth's geophysical environment (at multiple scale levels) ... not just the bits which satisfy a particular variant of a speculative exo-life hypothesis. Randomness still plays a large role in it all, and certain processes can be 'tipped' at certain times. This 'tipping' can easily make or break the outcome of steady-state life/no-life. And we know this, for certain. Knowing this for certain, vastly increases the possibility space, and makes the possibility of exo-life emergence on a duplicate of Earth, a lot less certain.

    Remote detection of possibly biogenic exo-gases, as a means of inferring the possible presence of exo-life, erodes optimism of exo-life (once again), to near meaninglessness, because of this vastly expanded possibility space.

    Regards

  21. #81
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    Quote Originally Posted by Selfsim View Post
    I question the 'sense' in entertaining such a hypothesis if there can be no definitive resolution by means of verification. If an exo-atmosphere is light years distant, there can be no such resolution.
    At this stage I think the aim is not as you say "definitive resolution by means of verification", but rather to use the data that we can get to build a tentative model
    that could for instance help us estimate the prevalence of life in the galaxy. A model could also predict currently unforeseen new evidence not originally used in building it.

    To continue with a hypothesis which is neither verifiable nor falsifiable by practical means, seems destined to become an obsession.
    A hypothesis can also be tested by comparing its logical consequences with what is practically observable. For instance we might find that a planet supporting life according to our theory orbits a star with certain properties that cannot support life on such a planet. That would be an example of falsification due to contradictory evidence in terms of the theory.

    … I gotta call it like I see it (in this particular case) .. apologies for eliminating areas of grey in what I'm saying, but I really do think some folk have lost sight of practicality constraints. No matter how intense one's dream might be, some things simply aren't feasible. Retrieveing verification evidence over light-year distances is one of 'em.
    It's only a practicality issue if you actually want to find conclusive evidence of extrasolar life, but as I said the point is to build a model that might be useful in yet unforeseen ways.

    Ok .. so we live in a non-ideal world, where resouces are constrained. If there exists other options/tests/experiments which can be demonstrated to make tangible returns on the sole basis of exo-life exploration, which can be demonstrated to be practically verifiable and falsifiable, I'd have to prefer those alternatives.
    I don't know how far we are from actually detecting extrasolar planetary atmospheres, but I can imagine it being like a Kepler type project. It doesn't seem that far fetched though.

    I don't have a problem acknowledging the spin-off benefits (eg: technological etc), derived from pursuing a dream, but these can also be obtained by pursuing more practical options ..
    The possibility exists that even after Mars, Europa and Titan have been thoroughly explored we won't have any exolife to study in detail. So the planetary exploration program is probably not the most economic way to get an idea of the prevalence of life in the galaxy at large.

    At the moment I think the best way to go about is to build computer models of, say solar system formation and planetary formation from Kepler type missions and then to combine such models with a theory of abiogenesis using data acquired from e.g chemical experiments and from whatever else we may know about the evolution of life here on Earth. I believe that understanding the general principles (not just contingent data) of abiogenesis is the key to solving the problem of the probability of life in general.

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    "To develop a model of Astrobiology, or not … that is the question" ….

    What is the true purpose of such a model ?

    If I was serious about finding exo-life, and I have the choice of either:

    i) going and looking for it, or;
    ii) developing a speculative, practically unverifiable model about it,

    What would I do ?

    My 2 cents worth: (i) above.

    Regards

    Footnote:
    As an attempt to contribute some factual data to this thread (beyond opinions), as far as our present remote exo-life bio-sign detection capability goes, a recently released (Nov 2011) paper claims confirmed detection of a strong 3.3 micron feature, (corresponding to the methane v3 branch), in the atmosphere of HD 189733b (a hot Jupiter ~63 Lyrs distant). (Done by the Spex spectrograph at the NASA Infrared Telescope Facility, atop Mauna Kea). There are several other of these projects presently underway, or under consideration. Regards

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    it wasnt too long ago it was thought to be impossible to detect small rocky planets, yet here we are at the verge of finding many of them.

    I beleive spectroscopy of distant planetary atmospheres could one day provide evidence beyond a reasonable doubt that there is life. Take a look at the TED Talk done br Dr Garik Isrealian.

    I agree absolute proof would require contact or at least a visual.

    but I don't agree with the idea that "we can't prove it through spectroscopy, so why bother at all?" attitude -- finding convincing evidence of life elsewhere will fuel technology to one day get us there.

  24. #84
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    Quote Originally Posted by Selfsim View Post
    i) going and looking for it, or;
    ii) developing a speculative, practically unverifiable model about it,

    What would I do ?

    My 2 cents worth: (i) above.
    i) and ii) are not two mutually exclusive options as you seem to think. If you going to look for something it helps to form an idea of where and how to look for it. Having a model helps in this regard, otherwise you'll have to look everywhere, and that's not very practical is it?

    As an attempt to contribute some factual data to this thread (beyond opinions), as far as our present remote exo-life bio-sign detection capability goes, a recently released (Nov 2011) paper claims confirmed detection of a strong 3.3 micron feature, (corresponding to the methane v3 branch), in the atmosphere of HD 189733b (a hot Jupiter ~63 Lyrs distant). (Done by the Spex spectrograph at the NASA Infrared Telescope Facility, atop Mauna Kea). There are several other of these projects presently underway, or under consideration.
    So what do they do with this data? Perhaps scientists look at data like this and together with other data formulate models.

    We confirm the previously reported strong emission at ~3.3 microns and, by assuming a 5% vibrational temperature excess for methane, we show that non-LTE emission from the methane nu3 branch is a physically plausible source of this emission. We consider two possible energy sources that could power non-LTE emission and additional modelling is needed to obtain a detailed understanding of the physics of the emission mechanism.

    Science is not just about data collection. There's always an element of theorizing to explain stuff. And a theory can be wrong and scientists know this.
    Last edited by Paul Wally; 2012-Apr-25 at 10:26 PM.

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    Quote Originally Posted by Paul Wally View Post
    i) and ii) are not two mutually exclusive options as you seem to thing. If you going to look for something it helps to form an idea of where and how to look for it. Having a model helps in this regard, otherwise you'll have to look everywhere, and that's not very practical is it?
    The exclusivity arises when one considers the funding priorities and its impact on local exploration.

    (I get that such a model is intended to guide the search, specifically by narrowing the Kepler confirmed findings).

    As I outlined earlier on in this thread, the issue I'm raising is limited to the exo-life justification component of remote exo-atmospheric gas analysis projects:
    Quote Originally Posted by Selfsim
    So I should make it clear that the point being made here pertains only to the making of progress in the exo-life discovery goal.
    The reference 'database' for interpreting such remote measurements, is dependent on confirmed (verified) causality between exo-life and exo-gases. There is presently only one instance to draw from (Earth-life/Earth atmosphere). Direct ET communication, or a random chance local discovery of exo-life, are presently our only means for taking this data beyond an instance of one. Interpretation of remote exo-gas measurements, is dependent on data gathered through local exploration.

    Without this missing data, as you say, interpretation will be by means of inference only. Which is no different to what we already have. No progress on exo-life determination will have been made.

    Some folk are content to live with inference as a primary means for determining the existence of exo-life. Extraordinary scientific claims call for extraordinary scientific evidence, and this will be missing until other instances of exo-life are verified. There is a limit to what can be inferred from remote measurements over light-year distances.
    Quote Originally Posted by Selfsim
    So what do they do with this data? Perhaps scientists look at data like this and together with other data formulate models.
    We already have a standard model for Earth-based life. The quest for exo-life is to verify that model. We are at the next phase of the process, so we should be taking steps which directly support the next phases of achieving that goal.
    Quote Originally Posted by Selfsim
    Science is not just about data collection. There's always an element of theorizing to explain stuff. And a theory can be wrong and scientists know this.
    You generalise back to 'Science'. We need to distinguish exactly what the hunt for exo-life is about, and distinguish it from astrophysical science … because it is fundamentally different, due to vastly greater complexity of what we're looking for, and the targetted scale level.

    Regards

  26. #86
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    Quote Originally Posted by Selfsim View Post
    The exclusivity arises when one considers the funding priorities and its impact on local exploration.
    You're mixing up the issue of funding with that of choosing the best research methodology. By the looks of it, it does seem that local planetary exploration requires much more resources than exoplanet observatories, but then again with planetary exploration there is a broad range of scientific objections like just learning more about planets in general. As I said it's entirely possible that we find no life on any of the other planets in our solar system.

    (I get that such a model is intended to guide the search, specifically by narrowing the Kepler confirmed findings).

    As I outlined earlier on in this thread, the issue I'm raising is limited to the exo-life justification component of remote exo-atmospheric gas analysis projects:
    "Exo-life justification" is where my issue lies. Why are you focused on justification? If Exo-life is eventually discovered will you then be surprised? Since we already
    know that it's possible the issue is not to justify its existence but rather to find out how it is possible. So for me it's largely a theoretical problem of how the laws of nature make the emergence of life possible in the universe at large. Given that this is the problem statement, any empirical research must be directed at finding clues that would help solve this theoretical problem, rather directing it at justifying the existence of exo-life.

    The reference 'database' for interpreting such remote measurements, is dependent on confirmed (verified) causality between exo-life and exo-gases. There is presently only one instance to draw from (Earth-life/Earth atmosphere). Direct ET communication, or a random chance local discovery of exo-life, are presently our only means for taking this data beyond an instance of one. Interpretation of remote exo-gas measurements, is dependent on data gathered through local exploration.
    The Earth is not an instance,sample or datapoint, it's more like a whole planet where life has emerged somewhere in this galaxy. Indeed, if we could explain how life emerged here we can explain how it can emerge anywhere else. At the moment we haven't yet solved the theoretical problem of how life emerges.

    Without this missing data, as you say, interpretation will be by means of inference only. Which is no different to what we already have. No progress on exo-life determination will have been made.
    Again, you're focussed on exo-life justification.

    Some folk are content to live with inference as a primary means for determining the existence of exo-life. Extraordinary scientific claims call for extraordinary scientific evidence, and this will be missing until other instances of exo-life are verified. There is a limit to what can be inferred from remote measurements over light-year distances.
    We already have a standard model for Earth-based life. The quest for exo-life is to verify that model. We are at the next phase of the process, so we should be taking steps which directly support the next phases of achieving that goal.
    Do you really think the existence of exo-life is an extraordinary scientific claim? I think the quest for exo-life is more about learning more about it and the emergence of life in general than about justification of its existence.

    You generalise back to 'Science'. We need to distinguish exactly what the hunt for exo-life is about, and distinguish it from astrophysical science … because it is fundamentally different, due to vastly greater complexity of what we're looking for, and the targetted scale level.
    Exobiology is about the study of life on other planets, but since we're not likely to find any samples any time soon, the approach should be to do the most we can with the data we can find. By getting as much as possible information on other solar systems we can get an idea of how common the conditions for the existence of life as we understand it is.Then a theory could be formulated linking the process of solar system formation with the process of the formation of life as we understand it.

  27. #87
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    Quote Originally Posted by Paul Wally View Post
    As I said it's entirely possible that we find no life on any of the other planets in our solar system.
    Because precedent based empirical life tests exist, and must be applied locally, a null conclusion is practically feasible.
    The same cannot be said for remote testing over light-year distances.
    A null finding locally would be a big step forward in the hunt for exo-life.

    Quote Originally Posted by Paul Wally View Post
    "Exo-life justification" is where my issue lies. Why are you focused on justification? If Exo-life is eventually discovered will you then be surprised? Since we already
    know that it's possible the issue is not to justify its existence but rather to find out how it is possible. So for me it's largely a theoretical problem of how the laws of nature make the emergence of life possible in the universe at large. Given that this is the problem statement, any empirical research must be directed at finding clues that would help solve this theoretical problem, rather directing it at justifying the existence of exo-life.
    With respect, I don't think we're on the same wavelength just yet ..
    The justification of which I speak, is in reference to projects whose goal is remote spectroscopic/telescopic/spectropolarimetry of exo-planet atmospheric 'bio'-gases. The astrobiological elements of these projects, target development of speculative models, which can only be interpreted via inference.

    Even if an Earth-like planet is found with an atmosphere of O2, CH4, Nitrogen, CO2 and H2O, the conclusion can still only be inferred, and there is no feasible way to verify life on that planet (or otherwise).

    It is feasible to verify exo-life with local exploration projects in habitable zones, however .. and yet these projects

    Quote Originally Posted by Paul Wally
    Exobiology is about the study of life on other planets, but since we're not likely to find any samples any time soon, the approach should be to do the most we can with the data we can find. By getting as much as possible information on other solar systems we can get an idea of how common the conditions for the existence of life as we understand it is.Then a theory could be formulated linking the process of solar system formation with the process of the formation of life as we understand it.
    The field of Astrobiology stands alone in science as having the sole purpose of justifying the belief that its subject matter exists.

    {My underline}: We have no idea about when we might find 'samples' … about the only definitive statement than can be justifiably made, is that if we don't make the attempt, we'll never retrieve any 'samples' of exo-life.

    Regards

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    Quote Originally Posted by Selfsim View Post
    A null finding locally would be a big step forward in the hunt for exo-life.
    Maybe .. maybe not. I think it depends on the kinds of conditions at the site where we don't find life. Then some kind of inference will have to be drawn from that null observation ... but since you have a problem with drawing inferences how is it going to be a big step forward for you?

    With respect, I don't think we're on the same wavelength just yet ..
    The justification of which I speak, is in reference to projects whose goal is remote spectroscopic/telescopic/spectropolarimetry of exo-planet atmospheric 'bio'-gases. The astrobiological elements of these projects, target development of speculative models, which can only be interpreted via inference.
    I don't know what to make of this. Do you think that the projects are unjustified or the inferences drawn from the empirical results of these projects? If your issue is with the latter, you're welcome to present your own interpretation or possible explanations.

    Even if an Earth-like planet is found with an atmosphere of O2, CH4, Nitrogen, CO2 and H2O, the conclusion can still only be inferred, and there is no feasible way to verify life on that planet (or otherwise).
    Discovery of such a planet would be quite significant. Even if we cannot directly observe the cause of these gasses the problem remains to explain how they could arise. For example oxygen is a gas that must be dynamically sustained in some way on a terrestrial planet because it tends to combine with other elements on the surface.

    The field of Astrobiology stands alone in science as having the sole purpose of justifying the belief that its subject matter exists.
    I don't think that is true. Exobiologists already except that their subject matter exists and don't try to justify it. They're just trying to learn what they can about it from the very limited evidence available.

    By the way, the very term exobiology is very geocentric, it suggests two fields of biology terrestrial and extra-terrestrial. In reality there should be only one field of universal biology inclusive of all lifeforms. Earth biology is an instance of universal biology.

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    Quote Originally Posted by Paul Wally View Post
    Maybe .. maybe not. I think it depends on the kinds of conditions at the site where we don't find life. Then some kind of inference will have to be drawn from that null observation ... but since you have a problem with drawing inferences how is it going to be a big step forward for you?
    Ok ... I don't have any problems .. and I don't seek any big steps forward.
    The issue on the other hand, is that a null result of a directly applied life test, contributes to furthering knowledge of 'habitable zone' definitions.
    Quote Originally Posted by Paul Wally
    I don't know what to make of this. Do you think that the projects are unjustified or the inferences drawn from the empirical results of these projects? If your issue is with the latter, you're welcome to present your own interpretation or possible explanations.
    Ok ... I don't have any issues.
    In comparison with locally applied life-tests which have been demonstrated innumerable times over on Earth-life samples, (and thus constitute a well established, vast historical repository of verified results), remote exo-gas detection pales into virtual insignificance, when it comes to firmness of conclusions drawn. Remote spectrographic (etc) results are dependent on model assumptions. Direct LR metabolic/chirality/C12/C13 isotope ratio/C3/C4 fixing/habitat characterisation/microscopic inspection/specific life molecule testing is not feasible over light-year distances. Such direct tests, far exceed the resolution of the measurement of some remotely detected exo-atmospheric gas which may well be present for some reason other than life presence. Remote spectrographic detection's exo-life interpretive database cannot be shown to be applicable to a particular exo-planet/moon etc, until at least another similar correlated life instance/exo-atmosphere is discovered and confirmed.

    I'm starting to seriously wonder why this is such a problem to understand ?

    Quote Originally Posted by Paul Wally
    Discovery of such a planet would be quite significant. Even if we cannot directly observe the cause of these gasses the problem remains to explain how they could arise. For example oxygen is a gas that must be dynamically sustained in some way on a terrestrial planet because it tends to combine with other elements on the surface.
    Well that's one explanation of a dynamically sustainable mechanism .. and it is entirely Earth-centric. Whether or not 'evidence' of this mechanism is always solely indicative of the presence of life, is unknown.

    Quote Originally Posted by Paul Wally
    I don't think that is true. Exobiologists already except that their subject matter exists and don't try to justify it. They're just trying to learn what they can about it from the very limited evidence available.
    I'm sorry, Paul .. that statement requires some serious rethinking ... I'll leave you to it.

    Quote Originally Posted by Paul Wally
    By the way, the very term exobiology is very geocentric, it suggests two fields of biology terrestrial and extra-terrestrial. In reality there should be only one field of universal biology inclusive of all lifeforms. Earth biology is an instance of universal biology.
    We have a standard life/genetic code model. Whether this is universal or not, is what is being tested.

    Regards

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    Quote Originally Posted by Selfsim View Post
    The field of Astrobiology stands alone in science as having the sole purpose of justifying the belief that its subject matter exists.
    This sort of joke goes back at least to 1964. It appeared in George Gaylord Simpson's article "The Non-prevalence of Humanoids" (Science, Vol 143, 21 Feb 1964), where he explained in detail why he thought searching for life beyond Earth would be futile.

    I read thru his article in hard copy in an academic library not long ago. You can also read the first page free on-line via http://www.sciencemag.org/content/143/3608/769 but you do have to pay for the privilege of downloading the full article.

    Simpson's argument was not that he considered life beyond Earth unlikely. He argued that in practice it was not likely to be found by humans in the foreseeable future because:

    1. It was improbable that evolution on a different world would result in a species sufficiently human-like for radio SETI to give a positive result.
    2. He thought this solar system probably did not contain habitable environments beyond Earth for any sort of life.
    3. He thought that exo-planets probably existed, but that the limitations of our technology would prevent us from detecting them for the foreseeable future.

    Well, he was wrong about detection of exoplanets, in any case. Whether he was right about the solar system remains to be established.

    As for the point about unlikeliness of radio-users evolving on another world, it may be a valid argument against radio SETI projects; but it's hardly an argument against astrobiology as such.
    Last edited by Colin Robinson; 2012-Apr-29 at 12:33 AM. Reason: small addition for clarity

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