The presence of life brings many unexpected consequences.
On Earth, for instance, when cyanobacteria spread widely in ancient oceans more than two billion years ago, their production of increasingly large amounts of oxygen killed off much of the other anaerobic life present at the day because oxygen is a toxin, unless an organism finds ways to adapt. One of the first global ices followed because of the changed chemistry of the atmosphere.
Now a group of researchers at the University of Arizona has modeled a similar dynamic that could have potentially taken place on early Mars.
As the group reports in the journal Nature Astronomy, their work has found that if microbial life was present on a wetter and warmer ancient Mars — as some now think that it potentially was — then it would almost certainly have lived below the surface. The rock record shows that the atmosphere would then have consisted largely of carbon dioxide and hydrogen, which would have warmed the planet with a greenhouse effect.
By using a model that takes into account how processes occurring above and below ground influence each other, they were able to predict the climatic feedback of the change in atmospheric composition caused by the biological activity of these microbes.
In a surprising twist, the study revealed that while ancient Martian life may have initially prospered, its chemical feedback to the atmosphere would have kicked off a global cooling of the planet by the methanogen’s use of the atmospheric hydrogen for energy and the production of methane as a byproduct.
That replacement of hydrogen with methane ultimately would render its surface uninhabitable and drive life deeper and deeper underground, and possibly to extinction.
“According to our results, Mars’ atmosphere would have been completely changed by biological activity very rapidly, within a few tens or hundreds of thousands of years,” said Boris Sauterey, a former postdoctoral student at the University of Arizona who is now a fellow at Sorbonne Université in Paris. .
“By removing hydrogen from the atmosphere, microbes would have dramatically cooled down the planet’s climate.”… Read more