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Thread: What do you think is the most likely explanation for the Fermi paradox?

  1. #481
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    Quote Originally Posted by kzb View Post
    The thing is, going by current thinking on abiogenesis, this is precisely what we should find on Mars.
    At any rate we should find them if abiogenesis is as common as hypothesized.
    All experiments point to nucleic acids and amino acids as the starting point for life, and this goes for both Earth and Mars.
    After that the prokaryotes would develop along very similar lines. Conditions on early Mars were similar to those on early Earth.
    Mars is a great place to explore, simply because we know already that conditions have been similar to those on Earth. We have seen the evidence that liquid water once flowed on the surface, which suggests the temperature was in the "ideal" life (as we know it) forming zone. If the conditions are right and the chemistry is there then it would be plausible to assume abiogenisis would occur given enough time. If Mars gives up some evidence of life formation then this would be some evidence that abiogenisis could be common place. But to rule out panspermia as a major factor then we would need to find life elsewhere were the probability of life hitching a ride on a rock is less likely.

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    Quote Originally Posted by kzb View Post
    That's not what I am saying at all. I am just saying that it is going to be a lot more difficult than balance of probabilities arguments.
    Then please define what you mean by "reasonable doubt".
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    Quote Originally Posted by kzb View Post
    All experiments point to nucleic acids and amino acids as the starting point for life, and this goes for both Earth and Mars.
    I may be misunderstanding you, but how can there be experimental data on the evolution of life on Mars? We havenít found life there as gas as I know (and I think it would be big news if we did).


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    Quote Originally Posted by kzb View Post
    The thing is, going by current thinking on abiogenesis, this is precisely what we should find on Mars.
    At any rate we should find them if abiogenesis is as common as hypothesized.
    All experiments point to nucleic acids and amino acids as the starting point for life, and this goes for both Earth and Mars.
    After that the prokaryotes would develop along very similar lines. Conditions on early Mars were similar to those on early Earth.
    Oh, okay. Need to update my severely limited knowledge on this. Thank you.

    There's no proof that Martian life, should it exist or have once existed, would be similar in biochemistry to Earth life. However, this assumption is long held, with even Carl Sagan holding this view. I am thumbing through an old paperback, Henry Cooper's The Search for Life on Mars (1980), covering the Viking mission to Mars. The scientists went with testing for life having a similar biochemistry to Earth's because no one had any idea of what to test for if the two biochemistries were not alike at all. No one does even today. An amino-acid, DNA, etc. view on possible Martian life is almost the default for lack of an alternative. Thus the excitement currently about detecting methane gas on Mars, which would make existing life Earthlike.
    Last edited by Roger E. Moore; 2019-Jun-29 at 01:13 AM.

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    To my recollection, there have not been many attempts to explore exotic biochemistries. Nothing seems to work so well as proteins in water.

    One of the most intellectually stimulating articles I've read on the topic was also one of the vaguest: Isaac Asimov's "We, the In-betweens", published as chapter 21 in his science anthology Is Anyone There? (1967). Asimov briefly explored several alternatives:

    1. Proteins in liquid ammonia (cold planets)
    2. Complex fatty molecules in liquid methane
    3. Fluorocarbon molecules in liquid sulfur (hot planets)
    4. Silicone molecules in liquid sulfur

    None of these is applicable to Mars, so we revert back to proteins in water.

    As Titan has lakes and seas of liquid hydrocarbons, methane-based life is often suggested for it. That seems to be the short form of the story, as I've seen it.

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    Maybe all species soon develop hyperintelligent AIs but fail the very difficult problem of making them friendly?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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    Speaking of contamination by Earthly organisms, this note on radiation-resistant space-station mold is interesting in the extreme. Sure, it's because humans are aboard, but we let a little thing get by us on a Surveyor once. You've got to be careful. Crewed voyages to other worlds will be tricky.

    https://www.sciencemag.org/news/2019...uld-kill-human

    NOTE: This has to do with being able later to prove whether native life on a world we've visited is actually "native" or influenced by earlier probes.
    Last edited by Roger E. Moore; 2019-Jun-29 at 03:43 PM.

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    Quote Originally Posted by Roger E. Moore View Post
    To my recollection, there have not been many attempts to explore exotic biochemistries.
    In 2007, the National Academies Press in Washington published a detailed report about possible exotic biochemistries by John A. Baross and others, which can read free online. It is called The limits of organic life in planetary systems. Have you looked at this, Roger?

    Nothing seems to work so well as proteins in water.

    One of the most intellectually stimulating articles I've read on the topic was also one of the vaguest: Isaac Asimov's "We, the In-betweens", published as chapter 21 in his science anthology Is Anyone There? (1967). Asimov briefly explored several alternatives:

    1. Proteins in liquid ammonia (cold planets)
    2. Complex fatty molecules in liquid methane
    3. Fluorocarbon molecules in liquid sulfur (hot planets)
    4. Silicone molecules in liquid sulfur

    None of these is applicable to Mars, so we revert back to proteins in water.
    I'd agree that any life on Mars is likely to involve liquid water and carbon-based catalysts.

    Whether those catalysts would be proteins is another question...

    As Titan has lakes and seas of liquid hydrocarbons, methane-based life is often suggested for it. That seems to be the short form of the story, as I've seen it.
    Glad you mentioned Titan...

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    Quote Originally Posted by Colin Robinson View Post
    In 2007, the National Academies Press in Washington published a detailed report about possible exotic biochemistries by John A. Baross and others, which can read free online. It is called The limits of organic life in planetary systems. Have you looked at this, Roger?
    Thank you! Never saw it before, will check it ASAP!

    LATER: Downloaded!

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    Quote Originally Posted by Roger E. Moore
    There's no proof that Martian life, should it exist or have once existed, would be similar in biochemistry to Earth life. However, this assumption is long held,
    ..
    Quote Originally Posted by Roger E. Moore
    To my recollection, there have not been many attempts to explore exotic biochemistries. Nothing seems to work so well as proteins in water...
    ..
    Quote Originally Posted by Roger E. Moore View Post
    Speaking of contamination by Earthly organisms, this note on radiation-resistant space-station mold is interesting in the extreme. Sure, it's because humans are aboard, but we let a little thing get by us on a Surveyor once. You've got to be careful. Crewed voyages to other worlds will be tricky.

    https://www.sciencemag.org/news/2019...uld-kill-human

    NOTE: This has to do with being able later to prove whether native life on a world we've visited is actually "native" or influenced by earlier probes.
    All this highlights the unscientific, almost religiously based strategy NASA currently has adopted in space exploration for 'finding life which must be out there'.
    'Life' in that statement currently has only one scientific context .. and that is Earth's biosphere.

    Taking hypotheticals such as Titan methanogens (for eg) as already being real and dwelling on Titan .. just waiting for us to scrape them up in order to 'prove' such untested speculation, is precisely why no life testing experiments have been sent back to Mars since Viking ... 43 years ago now .. (at least that's one popular consipracy claim which at least has a some semblance of scientific/engineering credibility to it).

    Just because there's a fixation with finding 'life' beyond the contextual surroundings which provide its very meaning, does not mean that it exists beyond that context, for goodness sake.

    General exploration with the aim of surveying and documenting whatever there is to be observed (visually, to start with), can lead to the same outcome as loading up some rover with Earth-life detection equipment .. if there is something 'out there' at all to find .. What's the hurry all about?

    Sending probes loaded up with complex life-diagnostic equipment only slows down the exploration program ... and in more recent times, such equipment hasn't even been used onsite due to experimental design flaws brought on by a lack of data on the targetted environments. Viking and Curiosity SAM wet front end gear are two classic examples.

    Earth mold spores introduced by probes (for eg) becomes completely moot when there is no visual evidence of mold growths on some rock found on Titan or Mars and the probe sent there doesn't include highly sensitive biochemistry lab experiments. There's both a cost and complexity saving .. right there .. for starters.

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    Quote Originally Posted by Selfsim View Post
    ....
    All this highlights the unscientific, almost religiously based strategy NASA currently has adopted in space exploration for 'finding life which must be out there'.
    More accurately, they seek to find out IF life is out there.

    No way to do that without testing for life.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Colin Robinson View Post
    I'd agree that any life on Mars is likely to involve liquid water and carbon-based catalysts.

    Whether those catalysts would be proteins is another question...
    Its all the same question, given that the speculative hypothetical it is based on, posits the existence of the possibility that the premise might be true. Its not clear to me how agreement on a hypothetical premise is likely to influence the observation of some earth-life sign in an image taken of an in-situ specimen.

    Quote Originally Posted by Colin Robinson
    Glad you mentioned Titan...
    (Perhaps a more interesting topic) but what happens to mold spores in conditions such as Titan's? What kind of testable predictions does McKay's methanogen hypothesis make? What are his predicted impacts the drone will have on his hypothetical methanogen? How about the sub-surface drill sample equipment and process impacts expected in the upcoming Mars tests?

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    Quote Originally Posted by Noclevername View Post
    More accurately, they seek to find out IF life is out there.

    No way to do that without testing for life.
    The 'if' condition signifies a test in logic .. A conditional test in logic is .. well .. still logic ... Logic doesn't follow the same process as the scientific process .. there are funadmental differences in purpose, too .. But alas, that was the topic of a humungous thread you started .. in a time looong past! Peace brother!

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    Quote Originally Posted by Selfsim View Post
    The 'if' condition signifies a test in logic .. A conditional test in logic is .. well .. still logic ... Logic doesn't follow the same process as the scientific process .. there are funadmental differences in purpose, too .. But alas, that was the topic of a humungous thread you started .. in a time looong past! Peace brother!
    I cannot follow your logic here.

    What are you saying? That we should not test the hypothesis of ET life?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Selfsim View Post
    ....
    All this highlights the unscientific, almost religiously based strategy NASA currently has adopted in space exploration for 'finding life which must be out there'.
    'Life' in that statement currently has only one scientific context .. and that is Earth's biosphere.

    Taking hypotheticals such as Titan methanogens (for eg) as already being real and dwelling on Titan .. just waiting for us to scrape them up in order to 'prove' such untested speculation, is precisely why no life testing experiments have been sent back to Mars since Viking ... 43 years ago now .. (at least that's one popular consipracy claim which at least has a some semblance of scientific/engineering credibility to it).

    Just because there's a fixation with finding 'life' beyond the contextual surroundings which provide its very meaning, does not mean that it exists beyond that context, for goodness sake.
    You appear to be saying that everyone in NASA (or those directing NASA) believes life exists somewhere else. I am not sure if that is completely true, but I suspect some NASA people do think so. I have never seen anyone prove Titan has life, that's still theoretical, no evidence there.

    I don't understand your conspiracy claim.

    I would say yeah, sure, there's no proof life elsewhere exists, but lots of people would like an answer to that question, so we go searching. I'm not sure I understand what's wrong with that. If you are saying life exists only on Earth, sure, for right now that's what we do know, but no harm in looking around and speculating on it. That's good right there.
    Last edited by Roger E. Moore; 2019-Jun-29 at 11:40 PM.

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    Quote Originally Posted by Selfsim View Post
    Earth mold spores introduced by probes (for eg) becomes completely moot when there is no visual evidence of mold growths on some rock found on Titan or Mars and the probe sent there doesn't include highly sensitive biochemistry lab experiments. There's both a cost and complexity saving .. right there .. for starters.
    Hmm, here you seem to be saying that life exists on Earth only, and looking for it elsewhere is kind of dumb and a waste of time and money. Did I get that right?

    Should point out that many microbes live underground or inside rocks, not on rocks where UV and other radiation would kill them. This is seen in Antarctica, for instance, and microbes living deep underground has been a big deal in the science news lately. Could happen on Mars, but we don't know. Gotta look, right?

    https://en.wikipedia.org/wiki/Endolith

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    Quote Originally Posted by Selfsim View Post
    All this highlights the unscientific, almost religiously based strategy NASA currently has adopted in space exploration for 'finding life which must be out there'.
    That bold-faced part could have been better worded, as it makes unfounded accusations, but that's, like, just your opinion, man.

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    Quote Originally Posted by Selfsim View Post
    Earth mold spores introduced by probes (for eg) becomes completely moot when there is no visual evidence of mold growths on some rock found on Titan or Mars and the probe sent there doesn't include highly sensitive biochemistry lab experiments. There's both a cost and complexity saving .. right there .. for starters.
    Or, save 100% and not send probes at all! /sarcasm
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    Quote Originally Posted by Roger E. Moore View Post
    Hmm, here you seem to be saying that life exists on Earth only, and looking for it elsewhere is kind of dumb and a waste of time and money. Did I get that right?
    The way I interpreted Selfsimís comment was that it is wasteful to spend money on specialized equipment that is designed to detect life as we know it, but which might miss other clues because it is specialized, since this takes money away from more generalized surveys that might detect clues that we hadnít thought of.

    I understand the issue. I think part of the reason is the science funding process, where often you have to provide specific goals for an experiment.


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    Quote Originally Posted by Jens View Post
    The way I interpreted Selfsim’s comment was that it is wasteful to spend money on specialized equipment that is designed to detect life as we know it, but which might miss other clues because it is specialized, since this takes money away from more generalized surveys that might detect clues that we hadn’t thought of.

    I understand the issue. I think part of the reason is the science funding process, where often you have to provide specific goals for an experiment.
    Okay, if that was the point (the writing was murky), then sure, I understand. But you have to start somewhere, even if it isn't the best place. Maybe another nation or corporation will get it right. Or NASA will get it right later. It happens.

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    Quote Originally Posted by Jens View Post
    The way I interpreted Selfsimís comment was that it is wasteful to spend money on specialized equipment that is designed to detect life as we know it, but which might miss other clues because it is specialized, since this takes money away from more generalized surveys that might detect clues that we hadnít thought of.
    That would be a valid criticism of the Viking mission. Its biology package was specialised to detect earth-like life directly, and it was based on a working assumption that the Martian surface environment was more earth-like than we now know it to be.

    I understand the issue. I think part of the reason is the science funding process, where often you have to provide specific goals for an experiment.
    Is that necessarily a bad thing? Does science progress just by generalised surveys? Or also by trying to answer specific questions?

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    Quote Originally Posted by Colin Robinson View Post
    Is that necessarily a bad thing? Does science progress just by generalised surveys? Or also by trying to answer specific questions?
    No, not necessarily. I think the generally accepted idea in funding today is that there should be a balance of mission-driven projects and curiosity-driven projects.



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    Quote Originally Posted by Selfsim View Post
    (Perhaps a more interesting topic) but what happens to mold spores in conditions such as Titan's? What kind of testable predictions does McKay's methanogen hypothesis make? What are his predicted impacts the drone will have on his hypothetical methanogen? How about the sub-surface drill sample equipment and process impacts expected in the upcoming Mars tests?
    Interesting questions! I've done my best to answer in a new thread "Testable predictions about life on Titan".

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    Quote Originally Posted by Jens View Post
    The way I interpreted Selfsimís comment was that it is wasteful to spend money on specialized equipment that is designed to detect life as we know it, but which might miss other clues because it is specialized, since this takes money away from more generalized surveys that might detect clues that we hadnít thought of.

    I understand the issue. I think part of the reason is the science funding process, where often you have to provide specific goals for an experiment.
    Thanks .. pretty close to where I was coming from .. sort of like being too focused on possible microscopic bio-minerals and methane gas isotopes and not seeing totally new kind of currently unrecognisable towering 'forest' overhead(?)

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    Quote Originally Posted by Roger E. Moore View Post
    .. But you have to start somewhere, even if it isn't the best place.
    The point is, in an exo-Earth context; we don't really have any clue about whether or not there exists any such a thing as 'a best place' .. so a 'starting point', therefore, can't even be said to exist in advance of exo-Earth exploration.

    Categorisation of exo-environments is the real deal. What happens after that intitial categorisation, drives the decisions to be made (such as science payloads).

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    Quote Originally Posted by Selfsim View Post
    The point is, in an exo-Earth context; we don't really have any clue about whether or not there exists any such a thing as 'a best place' .. so a 'starting point', therefore, can't even be said to exist in advance of exo-Earth exploration.

    Categorisation of exo-environments is the real deal. What happens after that intitial categorisation, drives the decisions to be made (such as science payloads).
    Ideally, yes. I'm all in favor of Big Science for it's own sake, but sadly, it's just not practical to go joyriding the planets at this point in human history. So the decisions get made, and they don't get made at the scientist's level. You want to change that, write your Congressman (or whomever is the shot caller in your particular Space Program).
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    Quote Originally Posted by Selfsim View Post
    The 'if' condition signifies a test in logic .. A conditional test in logic is .. well .. still logic ... Logic doesn't follow the same process as the scientific process .. there are funadmental differences in purpose, too .. But alas, that was the topic of a humungous thread you started .. in a time looong past! Peace brother!
    Quote Originally Posted by Noclevername View Post
    I cannot follow your logic here.

    What are you saying? That we should not test the hypothesis of ET life?
    Still waiting on Selfsim's answer.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername
    Quote Originally Posted by SelfSim
    Quote Originally Posted by Noclevername
    More accurately, they seek to find out IF life is out there.

    No way to do that without testing for life.
    The 'if' condition signifies a test in logic .. A conditional test in logic is .. well .. still logic ... Logic doesn't follow the same process as the scientific process .. there are funadmental differences in purpose, too .. But alas, that was the topic of a humungous thread you started .. in a time looong past! Peace brother!
    I cannot follow your logic here.

    What are you saying? That we should not test the hypothesis of ET life?
    ...
    Quote Originally Posted by Noclevername View Post
    Still waiting on Selfsim's answer.
    Well .. ok .. since you insist .. (we're a little OT though .. so I'll be brief).
    The phrase 'ET life' has no objective context .. therefore it has no objective meaning .. therefore the conditional logic test (denoted by the use of the 'If') , is testing for something that has no objective meaning and logic alone cannot return anything more than the 'truth' value of the original posit (which had no objective meaning). There is no objective evidence supporting 'ET life' as equating with 'Earth life' (the latter of which is of course, abundantly objectively evidenced).

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    Quote Originally Posted by Jens View Post
    I may be misunderstanding you, but how can there be experimental data on the evolution of life on Mars? (1) We haven’t found life there as gas as I know (and I think it would be big news if we did) (2).


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    (1) It's absolutely built-in to our current belief system. Lab experiments passing electric discharges through the assumed early Earth (and therefore Early Mars) atmosphere produce nucleic acids and amino acids. Since early Mars was pretty similar to Early Earth it is reasonable to assume the early life would be pretty similar. It's another principle of mediocrity argument. Experiments designed to detect life on Mars go with this reasoning also, as pointed out by Roger.

    (2) We have found life on Mars, and it was announced by the president of the United States on TV. This is a good example of the problems I anticipate.

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    Quote Originally Posted by Selfsim View Post
    ...
    Well .. ok .. since you insist .. (we're a little OT though .. so I'll be brief).
    The phrase 'ET life' has no objective context .. therefore it has no objective meaning .
    Bunkum.

    The problem is, since we don't know what ET life may or may not be like, we start with what we know works, and branch off from there. Start with detectable specifics, and then widen our search. If biological life under Earth conditions has certain characteristics, we extrapolate from known patterns such as water, and expand to other solvents, etc. It's a known, viable exploratory method; similar to what was used in WWII to search for lost ships or downed aircraft; Start from the last known location, and look further afield methodically.

    Suppose we do come across an unknown form of life or something similar to life, with no commonality to our own. How would we know to identify it unless we had a more general and broad definition of the terms life and lifelike, than what we currently use for ourselves?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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