5 ms·

Over the course of the past 2 decades we've gone from "perhaps some day we'll find extra solar planets" to "most if not all stars have planets". JWST's already

by loxias 4y ago

Over the course of the past 2 decades we've gone from "perhaps some day we'll find extra solar planets" to "most if not all stars have planets". JWST's already found water. At this point it's no longer a matter of if but when extrasolar life will be confirmed, and with which instrument. Might be JWST, might be WFIRST, might be HabEx.

adastra22 4y ago
By the standards of astrobiology, none of those instruments are capable of detecting life. But they might detect telltale signatures of biosphere in extrasolar atmospheres, which will trigger decades of debate as to whether there is life.
- loxias 4y ago
  I am not a biologist. I could be entirely wrong in which case please educate me. :) My understanding was that life would be "detected" by finding chemical signatures in the atmosphere which could not exist at a "steady state" without biological creatures there doing things. Is this what you mean by telltale signatures? (A++ username)
  - adastra22 4y ago
    Yes, astrobiologists distinguish between direct detection of life and biosignatures. The latter are things for which we don’t have non-biological explanations at this time, but which we don’t consider adequate evidence by themselves for life. FWIW we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions). And maybe Venus, though that is less clear. (Thanks!)
    - loxias 4y ago
      Thanks for this, your phrasing makes the concept more clear. Can you give a (fictitious as necessary) example of what would constitute "direct detection of life", from an astrobiological perspective? Given our window to the universe is through telescopes I'm having difficulty imagining/distinguishing how to draw the line between "observed data for which we don't have any non-biological explanation" and something even stronger. Like, does "direct detection of life" only include "we sent something there and found life"? > we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions). And ~Europa~ Enceladus too, right? ~ISTR seeing some paper about plumes of water vapor, as well as chemistry for which we don't have any non-biological explanation.~ I found it -- I was thinking of in 2017 when H2, CO2 and CH4 were detected at a ratio in thermodynamic disequilibrium . Edit: I'm guessing "direct detection" in an astrobiological context would be something that builds on "direct detection" in an exoplanet context, a concept I already understand a bit -- friend of mine wrote her thesis on direct detection and imaging of exoplanets 15 years ago. :)
      - TheOtherHobbes 4y ago
        https://astrobiology.nasa.gov/research/life-detection/ladder/ https://astrobiology.nasa.gov/research/life-detection/ladder...
        loxias 4y ago
        Yeah. I found and read that before my above comment (and skimmed some of the associated paper[1]) but all that says is direct detection hasn't been attempted since Viking, and that most good signals require in situ or sample return. It still doesn't answer my question! "astrobiologists distinguish between direct detection of life and biosignatures". The highest methods in terms of strength of evidence obtainable with remote sensing would be finding "deviations from thermodynamic equilibrium and/or kinetics" of "co-located reductant and oxidant" or "element or isotope fractionations indicative of metabolism". Which sound a whole lot like a detection of a biosignature, which "astrobiologists distinguish" from direct detection . :) I suspect direct detection in an astrobiological context must mean either "direct, as in we physically touched it" or maybe "a signature found using direct imaging". Definitions are hard. :) 1: https://www.liebertpub.com/doi/full/10.1089/ast.2017.1773 https://www.liebertpub.com/doi/full/10.1089/ast.2017.1773
        adastra22 4y ago
        Direct observation means, well, observing it directly. Seeing living cells in a microscope. Growing it in a Petri dish. Genetic testing, if it turns out it has DNA or RNA like us. Within our own solar system that generally means sample return, or sending people with a full biology lab. For an extrasolar planet? I don't think the astrobiology community is of a single mind regarding what should count as direct observation there. We're not sending people or doing sample return for thousands of years. One common opinion I've heard is that seeing an atmospheric spectrograph indicating the presence of biomarkers like oxygen and methane within the habitable zone would be a bio signature, but multi pixel imaging of the planet would be required to claim direct observation. I'm not sure this is a very strong scientific distinction, however. I'm not an astrobiologist btw, but I used to work at astrobiology.nasa.gov. Small world!
fullstackchris 4y ago
> At this point it's no longer a matter of if but when extrasolar life will be confirmed There is absolutely no data to confirm this, simply because no matter what equations or variables you throw around, we have no way of knowing the probability of life. We have only earth, and we still don't fully understand how that all worked out. We do not know what (or if!) any filter is present that prevents complex life. From a philisophical perspective, we'd be much better off as a species that the harder we look, we should hope to find _no_ life: https://nickbostrom.com/extraterrestrial.pdf https://nickbostrom.com/extraterrestrial.pdf
- loxias 4y ago
  I never claimed to have proof, just that it's true. ;-) Personally, it "feels true" that life exists as a undeniable consequence of statistical thermodynamics (see: http://www.englandlab.com/uploads/7/8/0/3/7803054/2013jcpsrep.pdf http://www.englandlab.com/uploads/7/8/0/3/7803054/2013jcpsre... referenced in https://www.quantamagazine.org/a-new-thermodynamics-theory-of-the-origin-of-life-20140122/ https://www.quantamagazine.org/a-new-thermodynamics-theory-o...). But I know I'm an engineer, not a scientist or mathematician. I'm perfectly comfortable with things being true even sans iron clad rigorous proof. If you limit your worldview to only that which has been rigorously proven you miss out on a lot of necessary and interesting truths, I think.
  - sammalloy 4y ago
    I always go back to people like Drake and Shostak. They seem pretty convinced that "they" are out there, but the problem is that there’s no known way to communicate with them due to distance and time. If there’s a way to solve this problem, please let me know. Sagan and others seemed to think that if we could communicate (a very big if), then we could exchange our knowledge, but how exactly could you do that? The problems appear insurmountable.
    - chmod775 4y ago
      Humanity has undertaken massive projects that took hundreds of years before (~2,000 years for all of the great wall of China). As long as they're less than a few thousands light years out, I don't think that communication would be impossible.
enkid 4y ago
Water is incredibly common in space, so doesn't really prove anything.
rich_sasha 4y ago
One thing that gives me pause for thought: even here on Earth, we are all, likely, descendants of a single organism: https://en.wikipedia.org/wiki/Last_universal_common_ancestor https://en.wikipedia.org/wiki/Last_universal_common_ancestor . It doesn't necessarily mean that the 0-1 creation of life happened exactly once on Earth (maybe it happened many times but the other lineages died out), but I think it makes this argument likely. We see a near-infinite menagerie of different organisms, from archaea and bacteria to reptiles and mammals, each finding its own niche, yet we don't see, on our own planet, any other blueprint for 0-1 life creation. Everything is DNA/RNA and cells, based on carbon and water, etc. And here we know conditions are just right, and we have studied the Earth like no other alien world. I'd expect, if the universe is in fact teaming with life, that we would see "aliens" on our own planet. But all we see is descendants of LUCA. It seems to me that either "life" is in fact vanishingly rare, or there's lots of other life forms we don't notice (including on Earth). My gut feeling is on the former.
- b800h 4y ago
  I think once you have one particular "life framework", it likely makes it super-difficult for other frameworks to develop in any major way.
  - rich_sasha 4y ago
    Maybe, but why? We have everything from archaea to mammals living and thriving alongside. Why not DNA life alongside non-DNA life? Is DNA-based life some kind of cosmic inevitability, like gravity? Or substitute for "DNA" any other common property of all life in Earth.
- lamontcg 4y ago
  It may be the 'LUCA' is very nearly the ideal early life form and RNA/DNA are the right way to do things. Just like water is pretty unique. Or alternatively, the first successful organisms on a planet out compete and literally eat the other organisms to extinction.

by loxias 4y ago

adastra22 4y ago

By the standards of astrobiology, none of those instruments are capable of detecting life. But they might detect telltale signatures of biosphere in extrasolar atmospheres, which will trigger decades of debate as to whether there is life.

loxias 4y ago
I am not a biologist. I could be entirely wrong in which case please educate me. :) My understanding was that life would be "detected" by finding chemical signatures in the atmosphere which could not exist at a "steady state" without biological creatures there doing things. Is this what you mean by telltale signatures? (A++ username)
- adastra22 4y ago
  Yes, astrobiologists distinguish between direct detection of life and biosignatures. The latter are things for which we don’t have non-biological explanations at this time, but which we don’t consider adequate evidence by themselves for life. FWIW we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions). And maybe Venus, though that is less clear. (Thanks!)
  - loxias 4y ago
    Thanks for this, your phrasing makes the concept more clear. Can you give a (fictitious as necessary) example of what would constitute "direct detection of life", from an astrobiological perspective? Given our window to the universe is through telescopes I'm having difficulty imagining/distinguishing how to draw the line between "observed data for which we don't have any non-biological explanation" and something even stronger. Like, does "direct detection of life" only include "we sent something there and found life"? > we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions). And ~Europa~ Enceladus too, right? ~ISTR seeing some paper about plumes of water vapor, as well as chemistry for which we don't have any non-biological explanation.~ I found it -- I was thinking of in 2017 when H2, CO2 and CH4 were detected at a ratio in thermodynamic disequilibrium . Edit: I'm guessing "direct detection" in an astrobiological context would be something that builds on "direct detection" in an exoplanet context, a concept I already understand a bit -- friend of mine wrote her thesis on direct detection and imaging of exoplanets 15 years ago. :)
    - TheOtherHobbes 4y ago
      https://astrobiology.nasa.gov/research/life-detection/ladder/ https://astrobiology.nasa.gov/research/life-detection/ladder...
      - loxias 4y ago
        Yeah. I found and read that before my above comment (and skimmed some of the associated paper[1]) but all that says is direct detection hasn't been attempted since Viking, and that most good signals require in situ or sample return. It still doesn't answer my question! "astrobiologists distinguish between direct detection of life and biosignatures". The highest methods in terms of strength of evidence obtainable with remote sensing would be finding "deviations from thermodynamic equilibrium and/or kinetics" of "co-located reductant and oxidant" or "element or isotope fractionations indicative of metabolism". Which sound a whole lot like a detection of a biosignature, which "astrobiologists distinguish" from direct detection . :) I suspect direct detection in an astrobiological context must mean either "direct, as in we physically touched it" or maybe "a signature found using direct imaging". Definitions are hard. :) 1: https://www.liebertpub.com/doi/full/10.1089/ast.2017.1773 https://www.liebertpub.com/doi/full/10.1089/ast.2017.1773
        adastra22 4y ago
        Direct observation means, well, observing it directly. Seeing living cells in a microscope. Growing it in a Petri dish. Genetic testing, if it turns out it has DNA or RNA like us. Within our own solar system that generally means sample return, or sending people with a full biology lab. For an extrasolar planet? I don't think the astrobiology community is of a single mind regarding what should count as direct observation there. We're not sending people or doing sample return for thousands of years. One common opinion I've heard is that seeing an atmospheric spectrograph indicating the presence of biomarkers like oxygen and methane within the habitable zone would be a bio signature, but multi pixel imaging of the planet would be required to claim direct observation. I'm not sure this is a very strong scientific distinction, however. I'm not an astrobiologist btw, but I used to work at astrobiology.nasa.gov. Small world!

fullstackchris 4y ago

> At this point it's no longer a matter of if but when extrasolar life will be confirmed There is absolutely no data to confirm this, simply because no matter what equations or variables you throw around, we have no way of knowing the probability of life. We have only earth, and we still don't fully understand how that all worked out. We do not know what (or if!) any filter is present that prevents complex life. From a philisophical perspective, we'd be much better off as a species that the harder we look, we should hope to find _no_ life: https://nickbostrom.com/extraterrestrial.pdf https://nickbostrom.com/extraterrestrial.pdf

loxias 4y ago
I never claimed to have proof, just that it's true. ;-) Personally, it "feels true" that life exists as a undeniable consequence of statistical thermodynamics (see: http://www.englandlab.com/uploads/7/8/0/3/7803054/2013jcpsrep.pdf http://www.englandlab.com/uploads/7/8/0/3/7803054/2013jcpsre... referenced in https://www.quantamagazine.org/a-new-thermodynamics-theory-of-the-origin-of-life-20140122/ https://www.quantamagazine.org/a-new-thermodynamics-theory-o...). But I know I'm an engineer, not a scientist or mathematician. I'm perfectly comfortable with things being true even sans iron clad rigorous proof. If you limit your worldview to only that which has been rigorously proven you miss out on a lot of necessary and interesting truths, I think.
- sammalloy 4y ago
  I always go back to people like Drake and Shostak. They seem pretty convinced that "they" are out there, but the problem is that there’s no known way to communicate with them due to distance and time. If there’s a way to solve this problem, please let me know. Sagan and others seemed to think that if we could communicate (a very big if), then we could exchange our knowledge, but how exactly could you do that? The problems appear insurmountable.
  - chmod775 4y ago
    Humanity has undertaken massive projects that took hundreds of years before (~2,000 years for all of the great wall of China). As long as they're less than a few thousands light years out, I don't think that communication would be impossible.

enkid 4y ago

Water is incredibly common in space, so doesn't really prove anything.

rich_sasha 4y ago

One thing that gives me pause for thought: even here on Earth, we are all, likely, descendants of a single organism: https://en.wikipedia.org/wiki/Last_universal_common_ancestor https://en.wikipedia.org/wiki/Last_universal_common_ancestor . It doesn't necessarily mean that the 0-1 creation of life happened exactly once on Earth (maybe it happened many times but the other lineages died out), but I think it makes this argument likely. We see a near-infinite menagerie of different organisms, from archaea and bacteria to reptiles and mammals, each finding its own niche, yet we don't see, on our own planet, any other blueprint for 0-1 life creation. Everything is DNA/RNA and cells, based on carbon and water, etc. And here we know conditions are just right, and we have studied the Earth like no other alien world. I'd expect, if the universe is in fact teaming with life, that we would see "aliens" on our own planet. But all we see is descendants of LUCA. It seems to me that either "life" is in fact vanishingly rare, or there's lots of other life forms we don't notice (including on Earth). My gut feeling is on the former.

b800h 4y ago
I think once you have one particular "life framework", it likely makes it super-difficult for other frameworks to develop in any major way.
- rich_sasha 4y ago
  Maybe, but why? We have everything from archaea to mammals living and thriving alongside. Why not DNA life alongside non-DNA life? Is DNA-based life some kind of cosmic inevitability, like gravity? Or substitute for "DNA" any other common property of all life in Earth.
lamontcg 4y ago
It may be the 'LUCA' is very nearly the ideal early life form and RNA/DNA are the right way to do things. Just like water is pretty unique. Or alternatively, the first successful organisms on a planet out compete and literally eat the other organisms to extinction.