The question of life on Mars is an open one. One approach to finding information is to look at the Red Planet’s past and estimate if and when it ever had conditions suitable for life. A new study says that in the distant past, methane-producing bacteria that fed on hydrogen may have lived beneath the surface of Mars. If they did exist, we are in a good place to find evidence.

Scientists took a look at Mars about 3.7 billion years ago. This is a complicated epoch in the geological history of the planet, called the Noachian epoch. It was before the extensive volcanism that formed features like Olympus Mons, the tallest volcano in the Solar System. Oceans and rivers probably covered the planet and ice on the planet’s surface.

Water isn’t enough to make a world habitable, but it sure helps. The simulations revealed that the planet had the right conditions for life, but only below the surface, he writes IFL Science.

Methane-producing bacteria may have flourished beneath the surface of Mars

The soil would have been saturated with salt, protecting the microorganisms from ultraviolet rays and cosmic rays, while also providing water. Computer models show that simple microorganisms would have been able to survive and thrive, using molecular hydrogen and carbon dioxide to feed themselves. These are methane-producing bacteria.

It’s important to point out that the work looked at whether conditions were right for life, not whether life was present. However, the team believes that it is highly likely that the conditions allowed the microorganisms to exist. The major limiting factor is the extent of ice cover, which would have made life difficult.

If life had existed there, organisms would have risked extinction just by existing. The team estimates that, based on everything we know, methane-producing bacteria could have been enough to rival what we had in Earth’s oceans in the very distant past, and that’s a problem for life.

The Perseverance rover is in the right place

The absorption of hydrogen and the release of methane can trigger a global cooling event, causing the temperature to drop by tens of degrees. Even if early Mars had a temperate climate in parts, these microorganisms could have lowered it well below 0°C.

The hope for these microorganisms (if they existed and survived the global cooling event) would have been to retreat even deeper below the surface. This requirement suggests that if we were to look for the existence of these microorganisms, three places that would be good to study are Hellas Planitia, Isidis Planitia, and Jezero Crater. NASA’s Perseverance rover is studying Jezero Crater right now.

The work is published in Nature Astronomy.

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