Underground microbes may have swarmed ancient Mars

These simple life forms would have altered the atmosphere so profoundly that they triggered an Ice Age and snuffed themselves out.

Ancient Mars may have had an environment capable of harbouring an underground world teeming with microscopic organisms, French scientists reported on Monday.

But if they existed, these simple life forms would have altered the atmosphere so profoundly that they triggered a Martian Ice Age and snuffed themselves out, the researchers concluded.

The findings provide a bleak view of the ways of the cosmos. Life — even simple life like microbes — “might actually commonly cause its own demise", said the study's lead author, Boris Sauterey, now a post-doctoral researcher at Sorbonne University.

The results “are a bit gloomy, but I think they are also very stimulating”, he said in an email. “They challenge us to rethink the way a biosphere and its planet interact.”

In a study in the journal Nature Astronomy, Sauterey and his team said they used climate and terrain models to evaluate the habitability of the Martian crust some four billion years ago when the red planet was thought to be flush with water and much more hospitable than today.

They surmised that hydrogen-gobbling, methane-producing microbes might have flourished just beneath the surface back then, with several inches (a few tens of centimetres) of dirt, more than enough to protect them against harsh incoming radiation.

Anywhere free of ice on Mars could have been swarming with these organisms, according to Sauterey, just as they did on early Earth.