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Microbial activity in Martian analog soils after ionizing radiation: implications for the preservation of subsurface life on Mars

机译:电离辐射后火星模拟土壤中的微生物活性:对保护火星地下生命的影响

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摘要

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 in situ 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.
机译:目前,火星表面受到一系列因素的影响,这些因素可能阻止类地球生命的生存。但是,现代的行星演化概念认为这种存在对过去的生活气候更为有利。如果过去在火星上形成了一个生物圈,类似于起源于地球早期的生物圈,那么据推测,迄今为止,它一直以非生物状态保存在地球的肠中,就像居住在北极北极多年冻土中的微生物群落一样。和南极。在现代火星重排条件下,这种文物生命似乎被剥夺了赔偿损害的可能性(或者这些过程在地质时间尺度上发生),而电离辐射应被视为抑制这种无生命生命的主要因素。在本研究中,我们研究了从地球的两个不同极端生境中选择的土壤样本:南极干旱谷的古老多年冻土和摩洛哥山地沙漠的Xerosol土壤,在低压下以40 kGy剂量伽马射线辐照(1 Torr)和低温(−50°C)。居住在这些样品中的微生物群落对所施加的效应表现出高抵抗力,保留了大量活细胞,代谢活性和高生物多样性。根据结果​​,假定在目前的电离水平下,假定的生物圈可以在休眠状态下分别在火星重灰石的表层和5 m的深度分别保存至少50万年和800万年。辐射强度。

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