Impact shocked rocks as protective habitats on an anoxic early Earth
Impact shocked rocks as protective habitats on an anoxic early Earth
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DOI：
10.1017/s1473550414000123
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发表时间：
2015-01-01
影响因子：
1.7
通讯作者：
Cockell, Charles S.
中科院分区：
文献类型：
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作者：
Bryce, Casey C.;Horneck, Gerda;Cockell, Charles S.
在地球上，生活在强烈紫外线(UV)辐射压力下的微生物可以采用石器时代的生活方式，生长在岩石的裂隙和空隙中。微生物遇到的强烈紫外线照射会导致死亡和生物分子的重大破坏，这也严重降低了检测到生命迹象的可能性。在这里，我们展示了在国际空间站外22个月的紫外线辐射暴露期间，受到小行星或彗星撞击的多孔岩石为光养生物及其生物分子提供了保护。所使用的紫外光谱接近于早期地球等缺乏臭氧屏蔽的行星表面的高紫外线通量。这些数据证明，石器时代的栖息地可以为年轻行星上最糟糕的紫外线辐射环境提供避难所，并从经验上驳斥了这样一种观点，即早期强烈的紫外线辐射通量将阻止没有能力形成微生物垫或产生紫外线保护色素的光养生物在早期陆地的表面定居。
On Earth, microorganisms living under intense ultraviolet (UV) radiation stress can adopt endolithic lifestyles, growing within cracks and pore spaces in rocks. Intense UV irradiation encountered by microbes leads to death and significant damage to biomolecules, which also severely diminishes the likelihood of detecting signatures of life. Here we show that porous rocks shocked by asteroid or comet impacts provide protection for phototrophs and their biomolecules during 22 months of UV radiation exposure outside the International Space Station. The UV spectrum used approximated the high-UV flux on the surface of planets lacking ozone shields such as the early Earth. These data provide a demonstration that endolithic habitats can provide a refugium from the worst-case UV radiation environments on young planets and an empirical refutation of the idea that early intense UV radiation fluxes would have prevented phototrophs without the ability to form microbial mats or produce UV protective pigments from colonizing the surface of early landmasses.