Mars is hard to call a hospitable place. Despite the fact that the daytime temperature at the equator here in the summer can reach 35 degrees Celsius, its average for the planet is about -63 degrees. In this case, the poles at night it could go down to -145 degrees. The atmospheric pressure on Mars is 160 times lower than on earth. Yes… And here we are, in the opinion of some experts, will have to move in the future. Whatever it was, the scientific community continues to work and find ways to survive in this ice, radiation and the desert hell.
Latest news from the scientific front talking about the work of the staff of the biological faculty of MSU named after M. V. Lomonosov, who studied the resistance of microorganisms to cosmic radiation in low temperature conditions. Information about what researchers have come, was published in the journal Extremophiles.
Scientists comment that until now was not known what the limits of resistance of microorganisms to influence of extreme factors. But with the help of these limits we can find out the probability of preservation of life or at least biomarkers on various objects in the Solar system. Information is essential for planning astrobiological space missions where it is important to choose as the objects of study and methods of detecting life.
In their work the authors conducted a study of radioresistance (resistance to radioactive radiation, in other words) of microbial communities living in sediments under conditions of extremely low temperature and pressure. These rocks are considered to be the earthly analogue of the regolith is residual soil of Mars, exposed to a permanent space weathering. Scientists believe that if the red planet is life, then most likely it can be stored kryokonservierung condition and a key factor limiting the duration of this sound is the threshold of the accumulation of cells radiation damage. The definition of this limit will allow us to estimate the duration of the conservation of microorganisms in the regolith (if, of course, exist), including at different depths.
“We investigated the combined effects of physical factors (gamma radiation, low pressure, low temperature) on the microbial community of the ancient Arctic permafrost sedimentary rocks. The unique natural object — the ancient frozen rocks, not otchaivatsya about two million years. Overall, we conducted a simulation experiment to more fully reproduce the conditions of cryopreservation in the regolith of Mars. It is also important that the work investigated the effect of high doses of gamma radiation (100 kGy) on the viability of prokaryotes, while previously living prokaryotes were found at irradiation doses higher than 80 kGr” — shared one of the authors Vladimir chepcov, is a graduate student in the Department of soil biology, faculty of biology, Moscow state University.
To simulate the impact of these factors on the living organisms the researchers used a specially created climatic chamber that create and maintain a low pressure and temperature during gamma irradiation. The object of the study was used a natural microbial community, but not pure cultures of microorganisms grown in the laboratory.
The experiment showed that these communities have a high resistance to simulated extreme conditions of the Martian environment. Scientists say that after irradiation the total number of cells of prokaryotes and number of metabolically active bacterial cells remained at the control level, the number of cultivated bacteria (bacteria that grow on nutrient media) was reduced tenfold, and the number of metabolically active cells of archaea decreased three times. But the decrease in the number of cultured cells in the experiment due to a change in their physiological state, not death.
In a sample of soil taken from permafrost and exposed, the researchers found a high diversity of bacteria, but after irradiation the structure of the microbial community changed significantly. In particular, populations of actinobacteria of the genus Arthrobacter, which were not detected in the control samples, became dominant in the bacterial communities after exposure to a simulated extreme conditions. Scientists suggest that it was caused, most likely, some reduction in the number of cells in the dominant populations of bacteria, whose place was taken by actinobacteria of the genus Arthrobacter. The authors also conclude that bacteria of this genus are more resistant to the effects of the investigated conditions. In an additional studies scientists have proven that these bacteria exhibit very high resistance to UV radiation and radiation and their DNA is well preserved in ancient permafrost sediments for millions of years.
“The results of the study indicate the possibility of prolonged preservation of viable microorganisms in Martian regolith. The intensity of radiation on the surface of Mars is 0,05-0,076 G/year and decreases with depth. Given the intensity of the radiation in the regolith of Mars, the obtained data suggest the preservation of a hypothetical ecosystem on Mars analiticheskom condition in the surface layer of regolith (protected from UV rays) for a period of not less than 1.3-2 million years at a depth of two meters, not less than 3.3 million years at a depth of five metres — not less than 20 million years. The data obtained can also be applied to assess the possibility of detecting viable micro-organisms on other Solar system objects and inside small bodies in outer space,” adds the scientist.
In addition, the importance of the work lies in the fact that its the authors first proved the possibility of survival of prokaryotes under irradiation by ionizing radiation in doses more than 80 kGy. Empirical evidence suggests as a possible underestimation of the radiation resistance of the natural microbial communities and the need to study the synergistic effects of the totality of the alien and space factors on living organisms and biomolecules in astrobiology experiments.
The study was conducted in collaboration with scientists from the space research Institute of RAS, Physical-technical Institute named after A. F. Ioffe RAS, Saint-Petersburg state Polytechnic University Peter the Great, the Urals Federal University and St. Petersburg Institute of nuclear physics named after B. P. Konstantinov National research center “Kurchatov Institute”.