Cheptsov Vladimir S, Vorobyova Elena A, Osipov George A, Manucharova Natalia A, Polyanskaya Lubov' M, Gorlenko Mikhail V, Pavlov Anatoli K, Rosanova Marina S, Lomasov Vladimir N
Soil Science Faculty, Lomonosov Moscow State University, Moscow, Russia.
Space Research Institute, Russian Academy of Sciences, Moscow, Russia.
AIMS Microbiol. 2018 Jul 9;4(3):541-562. doi: 10.3934/microbiol.2018.3.541. eCollection 2018.
At present, the surface of Mars is affected by a set of factors that can prevent the survival of Earth-like life. However, the modern concept of the evolution of the planet assumes the existence more favorable for life climate in the past. If in the past on Mars had formed a biosphere, similar to the one that originated in the early Earth, it is supposed that it is preserved till now in anabiotic state in the bowels of the planet, like microbial communities inhabiting the ancient permafrost of Arctic and Antarctic. In the conditions of modern Martian regolith, this relic life seems to be deprived of the possibility of damage reparation (or these processes occur on a geological time scale), and ionizing radiation should be considered the main factor inhibiting such anabiotic life. In the present study, we studied soil samples, selected in two different extreme habitats of the Earth: ancient permafrost from the Dry Valleys of Antarctica and Xerosol soil from the mountain desert in Morocco, gamma-irradiated with 40 kGy dose at low pressure (1 Torr) and low temperature (-50 °C). Microbial communities inhabiting these samples showed high resistance to the applied effects, retained high number of viable cells, metabolic activity, and high biodiversity. Based on the results, it is assumed that the putative biosphere could be preserved in the dormant state for at least 500 thousand years and 8 million years in the surface layer of Mars regolith and at 5 m depth, respectively, at the current level of ionizing radiation intensity.
目前，火星表面受到一系列因素的影响，这些因素会阻碍类地生命的存活。然而，现代行星演化概念认为，火星过去存在对生命更为有利的气候。如果火星过去曾形成过一个类似于早期地球起源的生物圈，那么推测它至今可能以非生物状态保存在火星内部，就像栖息在北极和南极古老永久冻土中的微生物群落一样。在现代火星风化层的条件下，这种遗迹生命似乎失去了修复损伤的可能性（或者这些过程在地质时间尺度上发生），电离辐射应被视为抑制这种非生物生命的主要因素。在本研究中，我们研究了从地球两个不同极端栖息地选取的土壤样本：来自南极干谷的古老永久冻土和来自摩洛哥山区沙漠的旱成土，在低压（1托）和低温（-50°C）下用40千戈瑞剂量进行伽马辐照。栖息在这些样本中的微生物群落对施加的影响表现出高度抗性，保留了大量活细胞、代谢活性和高生物多样性。基于这些结果，推测假定的生物圈在当前电离辐射强度水平下，分别在火星风化层表层和5米深处可能以休眠状态保存至少50万年和800万年。
