Hydrogen-eating, methane-producing microbes called H2-based methanogens likely numbered among the earliest life forms on Earth, and still survive around deep-sea volcanic vents.

Now, new research in the journal Nature Astronomy suggests early Mars possibly provided living conditions favorable to similar lifeforms, though it does not say such lifeforms existed.

“We’re not dealing with a question of the origin of life on Mars,” said senior author Régis Ferrière of University of Arizona’s Department of Ecology & Evolutionary Biology. “We are saying, let's assume that conditions were there for life to appear, and then let's ask the question of whether this original life could have persisted.”

Whether a more temperate Mars — rich in carbon dioxide and hydrogen, and running with liquid water — could have sustained life 3.7 billion years ago remains widely debated.

But models simulating atmospheric and subsurface temperatures, chemistry and interactions support the possibility.

To stay alive, microbes would have had to occupy a kind of “Goldilocks zone” in the porous, brine-drenched crust, deep enough to stay warm and receive protection from cosmic radiation, but shallow enough to exchange gases with the atmosphere.

Ferrière says this interchange — pumping up atmospheric methane while guzzling down hydrogen — unfortunately would have caused a fatal global cooling within a few hundred thousand years.

“But some populations of microbes may have persisted deep underground,” he said. “The microbes may have migrated down deep in the crust where they could find a warmer temperatures.”

There, they might have adapted to use different energy sources, such as geochemical reactions or radiation.

Among other applications, the findings provide an educated guess of where life may have thrived during what experts call Mars’s Noachian Age.

“With such a model, you can take a map of Mars and start making species distribution models, as we would call them in ecology,” said Ferrière. “You can predict where to look for fossils of this early life.”

The authors suggest three areas with the highest probability for finding evidence of such microbes, one of which is Jezero crater, the site of NASA’s Perseverance rover mission.