The origin of methane on Mars “could either be life or geological activity – including volcanism,” says this 2009 article on BBC.
When Paris scientists Franck Lefevre and Francois Forget used a computer model of the Martian climate to reconstruct observations made on Earth, their model showed that the gas is unevenly distributed in the Martian atmosphere and changes with the seasons.
“The current chemistry as we know it is not consistent with the measurements of methane on Mars,” says Dr Lefevre, of the Universite Pierre et Marie Curie. “There is something else going on, something that lowers the methane lifetime by a factor of 600.”
If there is a much faster loss for methane on Mars, says Dr LeFevre, there must also be a much stronger production of methane.
In 2003, an American team used three different ground-based telescopes to monitor about 90% of Mar’s surface. The team identified “plumes” of methane. At one point, the primary plume contained an estimated 19,000 tonnes of the gas.
It is vital to understand how so much methane is produced and destroyed so quickly on the Red Planet, says Dr Michael Mumma, director of Nasa’s Goddard Center for Astrobiology.
Dr Mumma does not rule out a biological explanation for the phenomenon but says it is possible that geology alone could be responsible.
See entire article:
Thanks to Siligy for this link
So where does that methane come from? Not from humans, that’s for sure. And not rotting vegetation.
To paraphrase the late Dr. Thomas Gold of Cornell, I am sure that there are no big stagnant swamps on Mars.