Is there oxygen in Mars

Mars: enough oxygen for living things?

Could living things as we know them exist on Mars somehow and anywhere? Organisms that breathe oxygen are hardly an option, it has been said so far, because our neighboring planet has very little to offer of this earthly elixir of life. But now researchers are reporting: In liquid brine in areas close to the surface, amounts of oxygen could well dissolve, which theoretically enable aerobic respiration by microorganisms.

Life thrives on earth wherever three factors are present: liquid water, an energy source, and an oxidizer. Although there are alternatives to breathing in molecular oxygen (O2), most living things on earth use the advantages of this electron acceptor for their metabolism. But what about these three basic requirements in the case of Mars? It now seems clear that the red planet once had significant amounts of liquid water on its surface. But that was billions of years ago. Due to its current icy temperatures, which apparently only allow ice and no more liquids, Mars was considered to be absolutely bone dry for a long time.

The special "wet" of Mars in sight

But this is apparently not the case, as has meanwhile become apparent: there could be aqueous solutions at shallow depths under the surface of Mars that contain a high content of perchlorate and other salts that prevent freezing even when the values ​​are very low. To be able to exist in this frosty and “hot” broth would be a challenge for life - but it seems possible. Factor number one could therefore be present. As far as possible energy sources are concerned, it is known from Ede that some microorganisms can use minerals for their metabolism. This is also conceivable on Mars.

The researchers led by Vlada Stamenković from the California Institute of Technology in Pasadena have now dealt with factor number three. They investigated the question of whether oxygen concentrations could arise in the suspected brine in the subsurface of Mars, which would enable an aerobic metabolism. As they explain, there are very small amounts of oxygen in the area of ​​the surface, which result from the light-induced decomposition of carbon dioxide in the thin atmosphere. The researchers used these amounts as a basis for calculating the extent to which this oxygen could collect in perchlorate solutions under the pressure and temperature conditions of Mars.

Surprisingly rich in oxygen

The calculations by Stamenković and his colleagues show that, under the assumed conditions, the suspected liquids in the subsurface could reach surprisingly high oxygen concentrations. As the researchers explain, the values ​​are well within the range of what some microorganisms on earth need to maintain an aerobic metabolism. The researchers say that concentrations similar to those in terrestrial seawater could even develop. Perchlorate solutions, which may exist in the area of ​​the polar regions, could therefore be particularly rich in oxygen. The scientists explain that this is where the best temperatures prevail for the oxygen to pass into the liquids.

Whether there actually are Martian microbes, of course, remains completely open. But as the researchers emphasize, the results now show a little more life-friendly potential. “On earth, evolutionary development of aerobic respiration seems to have followed oxygen-producing photosynthesis. Our results now show that this may not necessarily have to be the case, as there may be other sources of O2. This now broadens our view of the possibilities for the existence of aerobes on alien celestial bodies, ”the researchers write.

Source: Nature Geoscience, doi: 10.1038 / s41561-018-0243-0

October 22, 2018

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