Early Mars could have been inhabited by methanogenic microorganisms

(ORDO NEWS) — Simulations have shown that under the surface of young Mars, conditions were as comfortable for primitive life as in the oceans of young Earth.

However, this did not last long, and the activity of microbes quickly depleted the atmosphere, making the planet uninhabitable.

Today’s Mars is a harsh desert, dry and cold, but it wasn’t always like that. In the distant past, the neighboring planet was relatively warm and humid, surrounded by a rather dense atmosphere rich in carbon dioxide and hydrogen, and in such conditions primitive life could well have arisen there.

“Conditions below the surface of early Mars could be suitable for the existence of methanogen microbes,” said the key author of the work, Regis Ferriere, a professor at the University of Arizona.

On Earth, such microorganisms obtain energy without oxygen, for example, from carbon dioxide and hydrogen, and methane is a by-product of these reactions.

They are considered among the oldest, although they are not so ubiquitous under current circumstances, often inhabiting the most extreme ecological niches – like “black smokers” at the bottom of the oceans.

However, on early Mars, about four billion years ago, during the Noachian period , conditions were much more suitable for the life of methanogens.

“We believe that at that time Mars was a little colder than Earth and nowhere near as cold as it is today, with average temperatures slightly above the freezing point of water,” says Regis Ferrier.

“We see early Mars as a rocky planet with a porous crust covered in liquid water that formed lakes and rivers, and perhaps even seas and oceans.”

Ferrier and his colleagues modeled the climate of the Red Planet during the Noach period, taking into account the abundance and high salinity of water (which is indicated by the analysis of ancient Martian rocks), the porosity of the surface, saturated with carbon dioxide and hydrogen of the atmosphere.

The scientists used these results to model the dynamics of ecosystems. The work made it possible to assess the possibility of the existence and development of life shallow under the surface of Mars.

The answer turned out to be positive: such conditions are capable of supporting the existence of methanogens (which was also indicated by some previous works).

According to scientists, it was too cold on the surface of the planet, but slightly below the temperature remained quite comfortable, and water, carbon dioxide and hydrogen seeping from above provided enough resources to extract energy through methanogenesis.

According to their estimates, optimal conditions persisted at depths of up to several hundred meters. “We found the very likely existence of subsurface life, which was limited only by the spread of ice (on the surface).

Biomass productivity could be comparable to the productivity of the oceans of the early Earth,” Ferrier added. However, this did not last long.

Modeling showed that if at first methanogenic life on Mars could flourish, then gradually it had an increasingly negative impact on the conditions of its own existence.

The biological activity of such microorganisms quickly – over hundreds or even tens of thousands of years – changed the composition and reduced the density of the Martian atmosphere.

The hydrogen content in it was rapidly falling, which could lead not only to an energy deficit, but also to the cooling of the entire planet.

As a result, Mars rapidly froze over and became uninhabited. Life could go deeper and deeper into the bowels, until the conditions there became completely unsuitable for it.


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