This may indicate that the rocks of Gale crater were formed in conditions similar to those on Earth. But in order to assert this, additional conditions are needed
TASS, January 17. The Curiosity rover measured the proportions of carbon isotopes in Martian methane molecules extracted from several dozen samples of Martian rocks. Its isotopic composition turned out to be close to the gas produced by terrestrial bacteria, the results of the study were published by the scientific journal Proceedings of the National Academy of Sciences.
"These samples are almost completely free of carbon-13, which makes them look like deposits of the oldest rocks of bacterial origin, which formed on the site of modern Australia 2.7 billion. years ago. So far, we cannot rule out that these deposits could have formed on Mars without the participation of living organisms," said Christopher House, one of the authors of the study, professor at the University of Pennsylvania (USA).
Curiosity found the first traces of methane on Mars in 2013. Subsequently, his instruments recorded several more large emissions of this gas, which, however, could not be confirmed by observations of orbiting Martian probes. Therefore, scientists have not come to a consensus about the existence of these emissions and their possible nature.
House and his colleagues tried to get an answer to the last question during the analysis of the chemical and isotopic composition of three dozen samples of Martian methane. They were obtained by the Curiosity rover as a result of heating rocks collected in different regions of Gale crater.
To the surprise of scientists, in a significant part, about 40%, of these samples, there was almost no carbon-13, which accounts for about 1% of the total mass of carbon on Earth. In the Martian rocks, its concentration was comparable to the carbon-13 fractions characteristic of terrestrial sedimentary rocks that arose in the distant past as a result of the activity of methanogenic microbes.
The absence of carbon-13 in such terrestrial rocks is due to the fact that the enzymes of living beings interact more actively with lighter carbon-12 atoms in the molecules of methane, carbon dioxide and various "bricks of life". This leads to the fact that the proportion of carbon-13 in the cells of living beings and in the rocks formed with their participation will be significantly lower than the values characteristic of inanimate nature.
It is not yet possible to say that the rocks from the Gale crater were formed under similar conditions. To do this, it is necessary to accurately measure the proportions of carbon isotopes in other samples of Martian rocks, as well as to study its circulation between the atmosphere and the lithosphere.
This is necessary to exclude the possibility that such ratios of carbon-12 and carbon-13 could not have arisen as a result of the interactions of Martian rocks and ultraviolet radiation, as well as the ingress of large amounts of carbon-12 to Mars from space. The absence of such evidence will allow scientists to begin the first serious search for traces of Martian life, House and his colleagues summed up.
