EVIDENCE FOR MICROBIAL LIFE ON MARS

Scientists have found evidence of the survival of microorganisms in the soil of Mars. The results of such studies are necessary for planning space missions – to assess the possibility of finding living conditions on celestial objects, to select regions where it would be possible to find organisms or their traces.

Scientists of the Department of Soil Biology of the Faculty of Soil Science at the Lomonosov Moscow State University (MSU) have found evidence of the survival of terrestrial-type microorganisms in the soil of Mars. MSU Faculty of Soil Science is the leading educational and scientific Center in Russia, which has been training specialists, bachelors, masters and highly qualified staff in soil science and ecology for more than 45 years. There are more than 300 employees, including 110 candidates and 56 doctors of Sciences. Applied and fundamental scientific research, educational activities and coordination of projects at the international level are carried out here in partnership with such structures as the Food and Agriculture Organization of the United Nations (FAO), the World Bank, centers and institutes of the Consultative Group for International Agricultural Research (CGIAR), etc.

MSU researchers for the first time studied the influence of high-concentration perchlorates on terrestrial analogues of hypothetical microbial communities of Mars. It turned out that a high concentration of perchlorates does not lead to death, but contributes to an increase in the number of many microorganisms. This indicates in favor of the possibility of survival of terrestrial-type microorganisms in the Martian regolith.
One of the main obstacles to the development of terrestrial microorganisms in the Martian conditions is the lack of liquid water. The average annual temperature on the planet is about -50°C, with fluctuations about from -150°C to +30°C depending on the region, season, time of day. At low temperatures water is in the form of ice, but at higher temperatures water sublimates, i.e. immediately turns into steam, because the atmospheric pressure on Mars is about 100 times lower than on Earth.
Thanks to space missions, it has been found that concentration of perchlorates about 0.5-1% are present in the Martian regolith (a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock). Scientists suggest that perchlorates may contribute to the formation and preservation of liquid water on Mars because their solutions have low freezing temperatures. Formation of relatively recently discovered on Mars geomorphological structures similar to streams, as well as subsurface water bodies, may be associated with formation of perchlorate-containing solutions. At the same time, perchlorates are strong oxidizing agents, and they can be detrimental to microorganisms. Earlier studies have shown that some microorganisms can grow in the presence of very high concentrations of perchlorates (over 10%). However, the limits of resistance of microorganisms to perchlorates have not been determined. Such studies have previously been conducted with individual microorganisms, while microorganisms generally exist as microbial communities in which different organisms interact both among themselves and with a heterogeneous environment.
The Faculty members studied the influence of high concentration perchlorates (5%) on microbial communities of desert soil and ancient frozen rock. Such microbial communities are considered as terrestrial analogues of hypothetical microbial communities of Mars, since they exist in extreme conditions. Soil and rock samples were moistened with a solution of perchlorates or water, then incubated for 10 days, and after that the number and diversity of microorganisms were studied. The scientists used methods of cultivation, epifluorescence microscopy, fluorescence hybridization in situ, multisubstrate testing, gas chromatography mass spectrometry of lipids. Preparation and incubation of samples, as well as the most microbiological analyses were carried out at MSU.
It turned out that the high concentration perchlorates did not lead to the death of the microbial community. Moreover, there was an increase in the abundance of many microorganisms and a large biodiversity comparable to that in samples without perchlorate. Thus, it is shown that the presence of 5% perchlorate in soils and rocks does not lead to the death or significant inhibition of microbial communities. This indicates in favor of the possibility of survival of terrestrial-type microorganisms in the Martian regolith.
The results of such studies are necessary to assess the possibility of finding living conditions on celestial objects, to select regions and/or types of rocks and landforms where it would be possible to find organisms or their traces. This, in turn, is required for the planning of space missions, for the development of methods and equipment for these missions, as well as for the development of planetary quarantine measures (i.e., preventing contamination of other planets and satellites by terrestrial microorganisms and vice versa).
Continuing the work, it is planned to study the influence of perchlorates of higher concentrations on microbial communities and search for maximum concentrations at which microbial communities can survive.
The results of research by Russian scientists were published in the “International Journal of Astrobiology”.