The subsurface of early Mars was likely habitable for microorganisms that feed on hydrogen and produce methane, according to a purely theoretical modeling study. published in Nature Astronomy. The predicted biomass production, had life existed, would have been comparable to that of Earth’s early ocean and had a global cooling effect on the planet’s early climate, the authors note in a press release.
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The possible habitability of early Mars, more than 3.7 billion years ago (at a time when life on Earth arose in parallel) has been widely debated. The evidence suggests that the planet harbored – at least during part of its history – potentially favorable conditions for the development of life. However, the probability of this scenario occurring has rarely been quantitatively established.
Boris Sauterey and his colleagues have modeled the interaction between the primitive environment of Mars and an ecosystem of so-called methanogenic hydrogenotrophs – microorganisms that survive by consuming hydrogen and producing methane – and which are considered to be one of the first forms of life on Earth. Land.
The authors’ theoretical simulations predict that the Martian crust was a viable location for this ecosystem – provided the surface was not entirely covered in ice – and could have produced biomass similar to that of Earth’s early ocean.
The team predicts that this ecosystem would have triggered a feedback event with the climate of Mars, globally cooling it by up to 40 degrees Kelvin and creating less habitable conditions near the surface. This would have forced microbes progressively deeper into the planet’s crust.
Looking ahead, the authors identify three locations: the Hellas Plain, the Isis Plain, and the Jezero Crater, as the best places to look for signs of this – so far theoretical – early methanogenic life near the surface of Mars.
“Excellent theoretical approach”
In statements to SMC Spain, Jesús Martínez Frías, planetary geologist and astrobiologist at IGEO (CSIC-UCM), considers that the study represents an “interesting exercise” and is an “excellent theoretical approach”; but he warns that there is no evidence of life on Mars or of its potential traces: “Although this hypothesis, or others, is not ruled out, there is no evidence of the existence of methanogens either now or in the past. In fact, there is a whole very interesting open debate about the actual existence (or not) of methane. I think this point should have been addressed in more detail, since the existing evidence about methane is still the subject of scientific debate.”
This expert recalls that from the missions currently underway on Mars, experimental data is being offered, both on the current geology, the atmosphere, the past geological record, the mineralogy and the geochemistry of Mars, including interpretations of paleoenvironments and habitability based on in all the previously indicated parameters: “I believe that these detailed analyzes will be the ones that will allow us to confirm or not in the future the validity and importance of the proposed model”.
César Menor Salván, Professor of Biochemistry at the University of Alcalá, also speaking to SMC, states: “Although, at first glance, it seems that the article tells us that Mars was habitable and that there was a high probability that life originated there, the authors suggest that the planet lost habitability early on the surface and in the areas closest to it, so, in the unlikely event that life on Mars had continued or that there is life today, it must be found in deep areas below the surface.