Life on Mars? Why It Matters
News today from NASA that they've confirmed the presence of methane in the Martian atmosphere, concentrated in three areas (one of the major sources, Nili Fossae, is shown here). For a variety of reasons, this offers the strongest evidence yet that Mars may have an active biology under the surface.
While both geology and biology can produce methane on Earth, inorganic production of methane is generally associated with volcanic and tectonic activity, none of which has been witnessed on Mars (it's clear that Mars was once geologically active, but there's little or no evidence of current vulcanism). In addition, the three source areas each have very different geologies, further complicating the argument that the methane comes from geological activity. Finally, the "serpentinization" process on Earth tends to plug up sources of methane. NASA's Lisa Pratt, one of the scientists delivering the press conference today, argues that while this isn't positive proof that the methane comes from biological activity, it does make the geological argument harder to sustain and makes the biological argument "more plausible."
An additional bit of complexity is that the methane seems to be leaving the Martian atmosphere faster than the chemical composition of the Martian environment would suggest. A biological process -- where the methane was being consumed by microbial life -- would fit the evidence. Follow-up research, unfortunately not possible with the current satellites and robots working Mars now, should be able to find more definitive (positive or negative) evidence.
So what would we have if we determined that there were microbes making methane, and other microbes consuming methane? An ecosystem -- the first ecosystem found someplace other than Earth.
This would be amazingly important for a variety of reasons, not the least of which being that we'd finally have a chance to do comparative ecology.
Everything we know about how ecosystems work, how biology works, comes from a single data point: Earth. And while there's quite a bit of diversity within the Earth's ecology, it's all based on more-or-less the same basic biological stuff. What would Martian microbes have as the equivalent of DNA? Genes? Would there be elements of their biochemistry that would be unusually surprising?
Then there's the possibility that said Martian microbes would have a biology essentially identical to that found on Earth. The most plausible explanation for that would be that Earth life actually started on Mars (which cooled faster than Earth, so would have started its biology sooner) and was exported via Martian rocks ejected from massive impacts and hitting Earth as meteorites. We've discovered Mars-origin meteorites on Earth, so we know this is plausible.
So many questions. Hopefully, NASA will get the funding it needs to look for the answers.