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It seems pretty unlikely that Earth life could accidentally seed any moon of Saturn, and extremely unlikely that it could out-compete life that's been adapting

by mcbits 9y ago

It seems pretty unlikely that Earth life could accidentally seed any moon of Saturn, and extremely unlikely that it could out-compete life that's been adapting to that environment for eons. As in, even less likely than Earth's surface bacteria hitching a ride on probes down to volcanic vents on Earth and out-competing the life there. Maybe it would find a small niche to fill. No matter how careful we are, if we do find life on another planetary body, genetically similar enough to be confused with present-day Earth life, the assumption should be that it is from Earth and there had been no other life. Unfortunately it leaves "are we alone?" unanswered, but it answers "can life exist beyond Earth?"

ceejayoz 9y ago
Cassini has an RTG, so a crash into something like Encaladus could potentially create a nice warm little oasis for Earth bacteria to live in. A few decades and some on the fringes of this oasis might adapt - there's believed to be liquid water there. Don't have to out-compete if there's nothing there, and being similar to Earth life wouldn't let us rule it out - rocks from asteroid impacts are known to have travelled between Earth and Mars, so it's not outrageous for one to have travelled between Earth and Saturn.
- mcbits 9y ago
  If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. That won't change, whether we crash a probe there or not. Finding extant life anywhere beyond Earth would still be a paradigm-shattering discovery, even if we must assume it arrived from Earth on a probe or ejecta. The probe we send to test for life must, of course, be completely sterile to ensure it's not detecting its own hitchhikers.
  - ceejayoz 9y ago
    > If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. Sure, and ruling that out is easier if we can say for certain we didn't crash an old space probe nearby.
    - mcbits 9y ago
      The only way it would help is if we had some other way to rule out asteroid impact ejecta but not probe contamination. So we'd have: 1) Life on Enceladus that's 2) genetically indistinguishable from Earth life, which 3) we know didn't travel on a rock, but 4) could have travelled on a probe. We're getting into teapot-orbiting-Mars territory.

by mcbits 9y ago

ceejayoz 9y ago

Cassini has an RTG, so a crash into something like Encaladus could potentially create a nice warm little oasis for Earth bacteria to live in. A few decades and some on the fringes of this oasis might adapt - there's believed to be liquid water there. Don't have to out-compete if there's nothing there, and being similar to Earth life wouldn't let us rule it out - rocks from asteroid impacts are known to have travelled between Earth and Mars, so it's not outrageous for one to have travelled between Earth and Saturn.

mcbits 9y ago
If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. That won't change, whether we crash a probe there or not. Finding extant life anywhere beyond Earth would still be a paradigm-shattering discovery, even if we must assume it arrived from Earth on a probe or ejecta. The probe we send to test for life must, of course, be completely sterile to ensure it's not detecting its own hitchhikers.
- ceejayoz 9y ago
  > If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. Sure, and ruling that out is easier if we can say for certain we didn't crash an old space probe nearby.
  - mcbits 9y ago
    The only way it would help is if we had some other way to rule out asteroid impact ejecta but not probe contamination. So we'd have: 1) Life on Enceladus that's 2) genetically indistinguishable from Earth life, which 3) we know didn't travel on a rock, but 4) could have travelled on a probe. We're getting into teapot-orbiting-Mars territory.