They grew microbes in Martian rock samples

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Researchers have grown extremophilic microbes in a small piece of a Martian meteorite. This work demonstrated that life could potentially exist under ancient Martian conditions.

As you probably know, a mission is in preparation to bring back Martian samples put aside by the rover Perseverance. However, it is important to remember that we already have Martian rocks on Earth. These were dislodged following impacts from meteorites, before traveling through the solar system to finally cross paths with our planet.

A small piece of this material has just been used for grow germs by researchers from the University of Vienna (Austria). The meteorite in question, named Martian Black Beauty, is a priceless stone formed from various pieces of Martian crust, some as old as 4.4 billion years, ejected millions of years ago from the surface of the Red Planet.

The goal: to determine whether or not a life form could survive and develop under ancient Martian conditions.

Extremophile organisms

The authors assumed that if life once existed on the Red Planet, then it probably looked like an extremophile. On Earth, these organisms are known to live in very hostile conditions.

In addition, we know that the atmosphere of ancient Mars was thick and rich in carbon dioxide. Here on Earth, organisms capable of fix carbon dioxide and convert inorganic compounds (such as minerals) into energy are known as chemolithotrophs. Also the researchers focused on this type of organisms. And on one species in particular: Metallosphaera renewed. This Archean is known to evolve in hot and acidic volcanic sources.

Cell growth

As part of this work, the researchers placed these organisms on the Martian mineral. Then, they put everything in a bioreactor carefully heated and gassed with air and carbon dioxide.

Under a microscope, the researchers were able to observe the growth of these organisms which, visibly, have adapted to this Martian environment. Analyzes also made it possible to evaluate the way in which these microbes had transformed the material in order to “build” new cells, leaving behind biomineral deposits composed of phosphates complexed with iron, manganese and aluminum.

“We have also observed the intracellular formation of crystalline deposits of a very complex nature (iron, manganese oxides, mixed manganese silicates)”, note the researchers. “However, these are unique growth characteristics that we had not observed before when cultivating these microbes on terrestrial mineral sources”.

M. sedula cells grown on a Martian meteorite. Credits: Milojevic et al., Communications Earth & Environment, 2021

Ultimately, these works could provide invaluable data in the search for ancient life on Mars. As said above, Perseverance is expected to probe these extraterrestrial biosignatures. Now that astrobiologists know what the crystalline deposits of Busy Marcus, they could potentially identify similar traits in the rover’s samples.

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