If there is life on Mars, it might just be below the surface

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Analysis of several Martian meteorites suggests that the subsoil of Mars could be a good place to search for possible current life on the Red Planet. When will a drilling operation be scheduled? Details of the study are published in the journal Astrobiology.

On Earth, the vast majority of living things need sunlight to develop and evolve, but there are organisms in the depths that can do without. To survive, these creatures rely on the byproducts of chemical reactions produced when rocks come into contact with water.

One of these reactions is the radiolysis. It occurs when radioactive elements contained in rocks react with water trapped in its pores. The water molecules are then found broken down into their constituent elements, namely hydrogen and oxygen. The released hydrogen eventually dissolves in the remaining groundwater, while minerals like pyrite absorb oxygen to form sulfated minerals.

Microbes can ingest dissolved hydrogen as fuel and use the oxygen stored in sulphates to “burn” this fuel. For example, at the bottom of the Kidd Creek mine in Canada, some of these creatures were isolated more than 1.5 km underground in water that hadn’t seen the light of day for over a billion years.

Similar conditions on Mars

As part of his doctorate, Jesse Tarnas and his team at Brown University sought to better understand these underground systems in an attempt to find out if similar habitats could be isolated on Mars.

For this work, the researchers relied on the composition data of several Martian meteorites representative of different parts of the planet’s crust. Analysis of these meteorites determined that if they were in constant contact with water, these rocks could indeed produce the chemical energy needed to support microbial communities similar to those that survive in the unlit depths of the Earth.

According to this work, the “ingredients” necessary for the development of life are particularly abundant in breccias of rocks more than 3.6 billion years old. Remember that unlike Earth, Mars is not subject to plate tectonics which constantly recycles crustal rocks (those that form the crust). Also, these plots of land, as old as they are, are probably largely still intact.

Photo taken by Perseverance on the 22 April 2021 (Sol 57). Credit: NASA / JPL-Caltech

Towards an exploration program by drilling?

Since these meteorites studied here are representative of the vast expanses of the Martian crust, the results suggest that much of Mars’ subsoil could be habitable.

The big implication here for the science of underground exploration is that wherever you have groundwater on Mars, there’s a good chance that you have enough chemical energy to support microbial life underground.“, Summarizes Jesse Tarnas. “We don’t know if life ever developed below the surface of Mars, but if so, we believe there is enough energy to sustain it until today.“.

For researchers, this new work pleads in favor of a exploration program by drilling aiming to search for signs of life in the Martian subsoil. We know that the planet once housed groundwater. Besides, there could be more. In July 2018, a team of astronomers announced the possible presence of a lake about twenty kilometers wide located 1.5 km deep under the Martian ice.

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