I know, i know. Mars is not an exoplanet. So I better keep away because this blog is only about exoplanets. But the prospect of life on Mars is irresistible to not think about, lest write about. So let's pretend the Mars is an exoplanet for now so I have a valid reason to write about it.
What do i think about the methane on Mars? Is it geological in nature, or biological? At this point, it can go either way. I could end this post with a 50/50 to play it safe. But that would be boring.
So i'll share what's on my mind: I have a 60% hunch that the methane is caused by microbes. 40% chance it is caused by geochemical means.
Let me give 2 clues why i think so.
First, Mars has no magnetic field. It may have little movement going on within it's interior by way of lava. That is why there are no active volcanos on Mars.
Second, there are microbes known to man that can thrive in temperatures as frigid as Mars. If "psychrotolerant" doesn't ring a bell, feel free to visit this discovery made by NASA scientists themselves way back in 2005. I think the Marsian organisms responsible for the methane are similar to Carnobacterium pleistocenium, an extremophile that can survive a frozen state.
The "seasonal" detection of methane may be due to the thawing of these hardy creatures. And you know what happens when microbes wake up during the warmer Martian summers - they eat, and fart (there goes your methane). Then they sleep again when the Martian winter sets in.
It will take years to send probes and dig up the site, or do some methane isotope-testing to settle the score. Until then, one thing i can suggest is to measure the seasonal methane emissions at exact intervals and see if they increase over time. If the level of seasonal methane increases every Martian year, then that could mean the population of microbes are increasing. Now that further increases the probability that the methane is indeed caused by, well...microbes.
If I'm wrong, well just remember: I was pretending that Mars was an exoplanet. Now if there are tons of Mars-like exoplanets out there, my scenario must be right in at least one of them!