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Can someone in the know please comment on the prospects for bacterial life on Mars? I know nothing about biology or astronomy, but the case for life on Mars se

by nyellin 15y ago

Can someone in the know please comment on the prospects for bacterial life on Mars? I know nothing about biology or astronomy, but the case for life on Mars seems extremely good. I'm basing this on: * Repeated offhand comments by Neil deGrasse Tyson (admittedly not a scientific source) * Articles in popular newspapers about "Mars Farts" (I haven't read any scientific publications on the topic) * Relatively recent (2009) reports about AL84001 (again, as understood by a layman) What are the accepted scientific opinions about those last two items?

cynest 15y ago
> astrology Astronomy is the correct word here. Astrology is horoscopes and the like.
- nyellin 15y ago
  Whoops, fixed that. Thanks.
jessriedel 15y ago
There is little likelihood of finding life on Mars or evidence that it existed in the past. If life was so easy to start that it arose independently on two planets in the same solar system, then we would expect it to start on literally billions of planets in the Milky Way. Since it would take much less than the age of the Milky Way to colonize it, we would expect the Milky Way to be colonized long ago (or for there to be some evidence that life arose elsewhere). There are a million caveats here. For instance, it's possible that life is easy to start but intelligent life is absurdly difficult to form. But this seems much less likely, given the development of life on Earth. Smart money is on no life. Here's a bit to get you started. http://en.wikipedia.org/wiki/Great_Filter http://en.wikipedia.org/wiki/Great_Filter
ChuckMcM 15y ago
I don't believe the 'prospects', a fairly imprecise term, have changed at all, however the probability that life has existed there has gone up substantially. Many scientists see liquid water as a pre-requisite for life because chemical processes that we associate with life happen in the presence of it. So the question of liquid water on Mars informs the probability of life there, no liquid water, lower probability, liquid water, higher probability. Much of the scientific community is on board with the idea that liquid water existed on Mars at 'some' time, and a few are in the 'recently' camp, and a small number are in the 'now' camp. It is subterranean, if it is there, because liquid water cannot exist under the current surface conditions. The 'farts' was the detection of the presence of methane in Mars' atmosphere. That is significant because methane is not stable in Mars' atmosphere and so unless it is being created some how it should not exist. Its presence, especially waxing and waning, says there is a mechanism on Mars that creates methane and releases it into the atmosphere. Now on Earth there are many biological processes which create methane and a few geological ones. The presence improves the probability that it may be caused by some form of bacteria but its creation is not required to be from biologic means. Much of the 'fossil' bacteria hoopla in the Mars meteorite was objected to on first principals (life has to exist there, prove that first). In light of its re-examination it is slightly more probable that it represents fossilized bacteria. So the argument in favor of their being life on (or under the surface of) Mars has picked up some facts to help out its case. It will remain a probability until such time as someone (or something) directly observes it. And of course someone else repeats that observation.

by nyellin 15y ago

cynest 15y ago

> astrology Astronomy is the correct word here. Astrology is horoscopes and the like.

nyellin 15y ago
Whoops, fixed that. Thanks.

jessriedel 15y ago

There is little likelihood of finding life on Mars or evidence that it existed in the past. If life was so easy to start that it arose independently on two planets in the same solar system, then we would expect it to start on literally billions of planets in the Milky Way. Since it would take much less than the age of the Milky Way to colonize it, we would expect the Milky Way to be colonized long ago (or for there to be some evidence that life arose elsewhere). There are a million caveats here. For instance, it's possible that life is easy to start but intelligent life is absurdly difficult to form. But this seems much less likely, given the development of life on Earth. Smart money is on no life. Here's a bit to get you started. http://en.wikipedia.org/wiki/Great_Filter http://en.wikipedia.org/wiki/Great_Filter

ChuckMcM 15y ago

I don't believe the 'prospects', a fairly imprecise term, have changed at all, however the probability that life has existed there has gone up substantially. Many scientists see liquid water as a pre-requisite for life because chemical processes that we associate with life happen in the presence of it. So the question of liquid water on Mars informs the probability of life there, no liquid water, lower probability, liquid water, higher probability. Much of the scientific community is on board with the idea that liquid water existed on Mars at 'some' time, and a few are in the 'recently' camp, and a small number are in the 'now' camp. It is subterranean, if it is there, because liquid water cannot exist under the current surface conditions. The 'farts' was the detection of the presence of methane in Mars' atmosphere. That is significant because methane is not stable in Mars' atmosphere and so unless it is being created some how it should not exist. Its presence, especially waxing and waning, says there is a mechanism on Mars that creates methane and releases it into the atmosphere. Now on Earth there are many biological processes which create methane and a few geological ones. The presence improves the probability that it may be caused by some form of bacteria but its creation is not required to be from biologic means. Much of the 'fossil' bacteria hoopla in the Mars meteorite was objected to on first principals (life has to exist there, prove that first). In light of its re-examination it is slightly more probable that it represents fossilized bacteria. So the argument in favor of their being life on (or under the surface of) Mars has picked up some facts to help out its case. It will remain a probability until such time as someone (or something) directly observes it. And of course someone else repeats that observation.