Terrestrial archaea, which produce methane, easily survive in Martian conditions, therefore, theoretically, this gas in the atmosphere of Mars can appear as a result of the activity of local microorganisms.
Scientists at the University of Arkansas (USA) have tested whether Methanothermobacter wolfeii, a species of archaea that consumes hydrogen and produces methane, can survive under the surface of Mars. It turned out that these archaea successfully divide under all conditions tested in the laboratory, simulating a stay on the Red Planet. The authors believe that this species is quite suitable for living in the lithosphere of Mars. Previously, it was found out that he can live on its surface in the area of water flows. Similar microorganisms are likely to produce methane on Mars. The study is reported on the university website.
The researchers subjected Methanothermobacter wolfeii to pressures of up to 1200 Earth atmospheres, heating to 55 degrees, and an ambient pH of 4.96 (acidic conditions) to 9.13 (highly alkaline conditions). In all these ranges, archaea not only did not die, but also divided intensively - faster than at normal pressure and pH. In an acidic environment, they multiplied the faster, the higher the pressure was; in an alkaline environment, after several hundred atmospheres, archaea slowed down their growth, but still did not stop it.
All models of the interior of Mars show that at a depth of 1 to 30 kilometers, the temperature and pressure do not go beyond the limits tested in this study in the laboratory. And the pH cannot be found out without geological surveys, but all practically conceivable compositions of the lithosphere of Mars should have it within the range tested in the experiment. This means that if there is hydrogen in the bowels of Mars (carbon dioxide gets there from the atmosphere), methanogens of this kind can thrive there.
Today it is known that there is a lot of water under the surface of Mars. On the surface, it is mainly represented by ice, but at a depth of 600 meters or more, it is warm enough for water to turn into a liquid form. In its presence, heated rocks undergo serpentinization - a process in which hydrogen is released. Methanogens absorb it and carbon dioxide, releasing methane as waste products.
The study is motivated by the fact that atmospheric methane has been found on Mars in recent years. It appears only in the warm season, and quickly disappears in the cold season. By itself, this gas is rapidly destroyed by ultraviolet light and cannot exist without replenishment from underground sources. On Earth, almost all methane is of biogenic origin, that is, it is created by living organisms-methanogens. This gave rise to suspicions that there are analogues of terrestrial methanogens on Mars. The new work shows for the first time that they can actually live in the depths of the planet, and withstand incredibly high pressure - more than at the bottom of the Mariana Trench.
Archaea are unicellular microorganisms that are separated from both bacteria and eukaryotes. They do not have a cell nucleus, nor any membrane organelles. Archaea are able to exist and multiply in conditions that are fatal for bacteria and any other organisms - for example, in water heated to 120 degrees.