There are two new possible indicators of life on Mars

The tenuous modern atmosphere of Mars seen from low-elevation orbit by NASA’s Viking 1

Two studies have taken different looks at at the potential for life on Mars, adding new theories to a long list about the red planet.

The first reports on the unusual form nitrogen takes in Martian rocks, which points to a previous era where the planet may have been more habitable.

The second paper discusses how carbon monoxide, an abundant gas in the martian atmosphere, could potentially support microbial communities.

Both studies are published in the journal PNAS (Proceedings of the National Academy of Sciences).

Indigenous fixed nitrogen in martian deposits

The Mars Science Laboratory Curiosity Rover has detected the presence of oxidised nitrogen-bearing compounds in deposits within Mars’s Gale Crater.

The nitrogen was in samples from three sites in more volume than could be accounted for from known sources.

The authors, led by Jennifer Stern of NASA Goddard Space Flight Centre, suggest that the nitrogen may have been released from decomposition of nitrates as the sample was heated during analysis.

The presence of nitrates in different types of deposits, representing both the martian dust and soil reservoir, and a potential ancient lakebed, suggests that the residues resulted from nitrogen fixation generated by thermal shock from lightning or impact on ancient Mars.

Terrestrial life requires a fixed form of nitrogen and the discovery of indigenous fixed nitrogen in Martian rocks and sediments has implications for the past habitability of Mars.

Carbon monoxide as potential energy source on Mars

Atmospheric carbon monoxide could potentially sustain microbial communities on Mars, the second study suggests.

Although the search for past or current life on Mars has focused primarily on finding liquid water, researchers have not identified an energy source which could fuel metabolism by microbes living on or near the planet’s surface.

Gary King of Louisiana State University suggests that carbon monoxide, an abundant gas in the Martian atmosphere, could potentially serve as a metabolic source at conditions likely found in the past and present.

Drawing parallels with locations on Earth such as the Bonneville Salt Flats in Utah, the author suggests that oxidation could occur on local scales in Martian brines, features thought to form seasonally and that explain narrow, dark-toned streaks observed from the Mars Reconnaissance Orbiter.

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