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The difference between nothing and micro-organisms is much greater than the difference between micro-organisms and macro-organisms. The discovery of non-terrest

The difference between nothing and micro-organisms is much greater than the difference between micro-organisms and macro-organisms. The discovery of non-terrestrial-origin micro-organisms in our solar system would be massively significant.

sfvisser 8y ago
Going from no life to simple life might actually be much easier than going from simple life to complex life. According to Nick Lane in The Vital Question: https://en.wikipedia.org/wiki/The_Vital_Question https://en.wikipedia.org/wiki/The_Vital_Question
- reubenswartz 8y ago
  Really enjoyed that book, and tend to agree, but it would still be pretty amazing to find microbes somewhere else....
  - thaumasiotes 8y ago
    > it would still be pretty amazing to find microbes somewhere else.... We already know two things with certainty: - a very small amount of material transits between Earth and Mars. - all material on Earth contains microbes. It would seem we also know that there are microbes on Mars, though at insignificant levels and likely not flourishing.
    - infradig 8y ago
      I thought meteorite transfer was one-way... Mars to Earth.
      - fsloth 8y ago
        Why? It seems to me the requirement is to have a mass with escape velocity from the parent body, and then have it’s orbit intercept another. The delta v required for the latter is symmetrical, from mars to earth. Hence, if a rock reaches escape velocity it would seem to me to be as easy to have pieces of earth rain on mars as it is to have mars fragments rain on earth. The impact on earth to cause ejecta to have escape velocity would probably need to be larger than on mars.
        knodi123 8y ago
        > The impact on earth to cause ejecta to have escape velocity would probably need to be larger than on mars. significantly larger, because it has to get through our atmosphere once on the way in, and then the ejecta has to do it again on the way out, keeping in mind that drag is proportional to velocity squared, and that whatever ejecta is making this trip has to find a way not to get cooked into sterility by impact energy or friction with the air.... Too many extra factors are in play, each of which adds an exponent to the unlikelihood. But that's just my uneducated opinion, I'm certainly open to discussion.
        simonh 8y ago
        The dV to get off Mars and to interplanetary transfer is about half that from Earth. I would expect the ejection energy of impact debris particles to scale with the square root of the impact energy, so you'd need four times the impact energy on Earth to achieve the same level of debris ejection as on Mars, and that's not counting the effect of Earth's atmosphere on cushioning and ameliorating such impacts. The dV to then end up on either planet doesn't matter because aerobraking and lithobraking do all the work for you.
      - thaumasiotes 8y ago
        Why? Earth gets hit by large meteors just like Mars does.
jolmg 8y ago
What is it about going from nothing to micro-organisms that is so much more interesting than from micro-organisms to macro-organisms?
- djohnston 8y ago
  because it's definitive proof that we aren't alone.
- jdblair 8y ago
  Because it poses new interesting questions: If extra-terrestrial life exists, do we have a common ancestor? This is the theory of panspermia. Or does life spontaneously arise when conditions are right, but with variation? It would be particularly exciting to discover life that is similar to Earth but with an opposite chirality, or a genetic code that encodes amino acids using different base pairs.
  - Baeocystin 8y ago
    I am willing to bet that whatever is eventually found will be remarkably similar to what we are familiar with on Earth, assuming a liquid-water environment, and the constraints that implies. Single-celled life appears to have arisen so rapidly that it predates the end of the Late Heavy Bombardment, after all. (I'd be thrilled to be wrong about this, of course, just as I would be fascinated with any xenobiological discovery at all. But I do think the 'endless forms most beautiful' are also strongly constrained by simple physics, and thus the solutions found by an evolutionary random walk will resemble what we already know.)
    - jolmg 8y ago
      This is what I suspect with microorganisms as well. Macroorganisms are much more complex and they have common features that seem very arbitrary like moving via cylindrical appendages called legs, or having faces that feature 2 eyes, a nose, and a mouth. It makes me think that it's much more likely to see something wildly different between macroorganisms on Earth and elsewhere than between microorganisms. It would be cool to see other forms of movement, other forms senses, other forms of communication, other forms of anatomy, etc. EDIT: It also makes me wonder how different an ecosystem could be. Imagine one that did not require macroorganisms eating other macroorganisms, like ones that feed on heat or wind. EDIT 2: Maybe mating requires 3 genders, etc. There seems to be a lot of room for variation.

sfvisser 8y ago

Going from no life to simple life might actually be much easier than going from simple life to complex life. According to Nick Lane in The Vital Question: https://en.wikipedia.org/wiki/The_Vital_Question https://en.wikipedia.org/wiki/The_Vital_Question

reubenswartz 8y ago
Really enjoyed that book, and tend to agree, but it would still be pretty amazing to find microbes somewhere else....
- thaumasiotes 8y ago
  > it would still be pretty amazing to find microbes somewhere else.... We already know two things with certainty: - a very small amount of material transits between Earth and Mars. - all material on Earth contains microbes. It would seem we also know that there are microbes on Mars, though at insignificant levels and likely not flourishing.
  - infradig 8y ago
    I thought meteorite transfer was one-way... Mars to Earth.
    - fsloth 8y ago
      Why? It seems to me the requirement is to have a mass with escape velocity from the parent body, and then have it’s orbit intercept another. The delta v required for the latter is symmetrical, from mars to earth. Hence, if a rock reaches escape velocity it would seem to me to be as easy to have pieces of earth rain on mars as it is to have mars fragments rain on earth. The impact on earth to cause ejecta to have escape velocity would probably need to be larger than on mars.
      - knodi123 8y ago
        > The impact on earth to cause ejecta to have escape velocity would probably need to be larger than on mars. significantly larger, because it has to get through our atmosphere once on the way in, and then the ejecta has to do it again on the way out, keeping in mind that drag is proportional to velocity squared, and that whatever ejecta is making this trip has to find a way not to get cooked into sterility by impact energy or friction with the air.... Too many extra factors are in play, each of which adds an exponent to the unlikelihood. But that's just my uneducated opinion, I'm certainly open to discussion.
      - simonh 8y ago
        The dV to get off Mars and to interplanetary transfer is about half that from Earth. I would expect the ejection energy of impact debris particles to scale with the square root of the impact energy, so you'd need four times the impact energy on Earth to achieve the same level of debris ejection as on Mars, and that's not counting the effect of Earth's atmosphere on cushioning and ameliorating such impacts. The dV to then end up on either planet doesn't matter because aerobraking and lithobraking do all the work for you.
    - thaumasiotes 8y ago
      Why? Earth gets hit by large meteors just like Mars does.

jolmg 8y ago

What is it about going from nothing to micro-organisms that is so much more interesting than from micro-organisms to macro-organisms?

djohnston 8y ago
because it's definitive proof that we aren't alone.
jdblair 8y ago
Because it poses new interesting questions: If extra-terrestrial life exists, do we have a common ancestor? This is the theory of panspermia. Or does life spontaneously arise when conditions are right, but with variation? It would be particularly exciting to discover life that is similar to Earth but with an opposite chirality, or a genetic code that encodes amino acids using different base pairs.
- Baeocystin 8y ago
  I am willing to bet that whatever is eventually found will be remarkably similar to what we are familiar with on Earth, assuming a liquid-water environment, and the constraints that implies. Single-celled life appears to have arisen so rapidly that it predates the end of the Late Heavy Bombardment, after all. (I'd be thrilled to be wrong about this, of course, just as I would be fascinated with any xenobiological discovery at all. But I do think the 'endless forms most beautiful' are also strongly constrained by simple physics, and thus the solutions found by an evolutionary random walk will resemble what we already know.)
  - jolmg 8y ago
    This is what I suspect with microorganisms as well. Macroorganisms are much more complex and they have common features that seem very arbitrary like moving via cylindrical appendages called legs, or having faces that feature 2 eyes, a nose, and a mouth. It makes me think that it's much more likely to see something wildly different between macroorganisms on Earth and elsewhere than between microorganisms. It would be cool to see other forms of movement, other forms senses, other forms of communication, other forms of anatomy, etc. EDIT: It also makes me wonder how different an ecosystem could be. Imagine one that did not require macroorganisms eating other macroorganisms, like ones that feed on heat or wind. EDIT 2: Maybe mating requires 3 genders, etc. There seems to be a lot of room for variation.