Ultraviolet (UV) irradiation on the surface of Mars is an important factor that affects the survivability of microorganisms on Mars. The possibility of martian brines made from Fe₂(SO₄)₃, MnSO₄, and MgSO₄ salts providing a habitable niche on Mars via attenuation of UV radiation was investigated on the bacteria Bacillus subtilis and Enterococcus faecalis. Results demonstrate that it is possible for brines containing Fe₂(SO₄)₃ on Mars to provide protection from harmful UV irradiation, even at concentrations as low as 0.5%. Brines made from MnSO₄ and MgSO₄ did not provide significant UV protection, and most spores/cells died over the course of short-term experiments. However, Fe₂(SO₄)₃ brines are strongly acidic and thus were lethal to E. faecalis, when cells were exposed for 7 days. In contrast, B. subtilis, a spore-forming bacterium resistant to pH extremes, was unaffected by the acidic conditions of the brines and did not experience any significant lethal effects in Fe₂(SO₄)₃. Any extant microbial life in martian Fe₂(SO₄)₃ brines (if present) would need to be capable of surviving acidic environments, if these brines are to be considered a possible habitable niche. The results from this work are important to the search for life on planets with atmospheres that do not significantly attenuate UV radiation (i.e., like Mars) and to planetary protection, since it is possible that terrestrial bacteria in the genus Bacillus are likely to survive in Fe-sulfate brines on Mars.

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模拟火星条件下枯草芽孢杆菌和粪肠球菌的耐盐性和紫外线防护

火星表面的紫外线（UV）照射是影响火星上微生物生存能力的重要因素。在枯草芽孢杆菌和粪肠球菌上研究了由 Fe ₂ (SO ₄ ) ₃、MnSO ₄和 MgSO ₄盐制成的火星盐水通过减弱紫外线辐射在火星上提供宜居生态位的可能性。结果表明，即使在浓度低至 0.5% 的情况下，火星上含有 Fe ₂ (SO ₄ ) _{3 的}盐水也可以提供免受有害紫外线辐射的保护。由 MnSO ₄和 MgSO制成的盐水₄没有提供显着的紫外线防护，大多数孢子/细胞在短期实验过程中死亡。然而，Fe ₂ (SO ₄ ) ₃盐水是强酸性的，因此当细胞暴露7天时对粪肠球菌是致命的。相比之下，枯草芽孢杆菌是一种能抵抗极端 pH 值的孢子形成细菌，不受盐水酸性条件的影响，并且在 Fe ₂ (SO ₄ ) _{3 中}没有经历任何显着的致死作用。火星 Fe ₂ (SO ₄ ) _{3 中}任何现存的微生物生命盐水（如果存在）需要能够在酸性环境中生存，如果这些盐水被认为是可能的宜居生态位。这项工作的结果对于在大气不会显着减弱紫外线辐射的行星（即像火星）上寻找生命和行星保护很重要，因为芽孢杆菌属的陆地细菌可能在火星上的硫酸铁盐水。