Early Mars may have been habitable for methane-producing microbes

Early Mars may have been habitable for methane-producing microbes

The primitive mars could have provided in the subsoil a favorable environment for the microbial life that feeds on hydrogen and produces methane, says a model-based study published today by Nature Astronomy.

The investigation headed by Boris Sauterey of the University of Arizona dates back to the Noachian period, over 3.7 billion years ago.

Until now, the evidence suggests that the red planet harbored – at least during part of its history – potentially favorable conditions for the development of life, however, science has rarely tried to quantitatively establish the probability of such a scenario.

The team presents a probabilistic evaluation of the habitability of mars for H2-based methanogens and quantifies their biofeedback on the Martian atmosphere and climate.

The result is that subsurface habitability was “very likely”, and was limited primarily by the extent of surface ice cover.

The team modeled the interaction between the primitive environment on Mars and an ecosystem of methanogenic hydrogenotrophs (microorganisms that survive by consuming hydrogen and producing methane), which are considered among the first life forms on Earth.

In Marsthe brine-saturated porous regolith would have created a physical space protected from ultraviolet and cosmic radiation and provided a solvent, the authors indicate in the study.

In addition, the temperature below ground and the diffusion of a dense, reduced atmosphere could have supported simple microbial organisms that consumed H2 and CO2 as energy and carbon sources and produced methane as waste.

The authors’ simulations predict that the Martian crust was a viable location for this ecosystem, as long as the surface was not entirely covered in ice.

In that case the biomass production predicted could have been comparable to that of Earth’s early ocean and have had a global cooling effect on Mars’ early climate, ending possible early warm conditions, compromising surface habitability and forcing the biosphere deeper in the Martian crust.

Spatial projections from the research indicate that lowland locations at low and mid-latitudes are good candidates for discovering traces of this early life at or near the surface.

In fact they identify three locations: Hellas Planitia, Isidis Planitia, and Jezero Crater (where NASA’s Perseverance rover is currently working), as the best places to look for signs of this early methanogenic life near the surface of Mars.

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