The Importance of Water for Life
The Importance of Water for Life
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DOI：
10.1007/s11214-018-0476-7
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发表时间：
2018-02
影响因子：
10.3
通讯作者：
F. Westall;A. Brack
中科院分区：
文献类型：
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作者：
F. Westall;A. Brack
正如我们所知，液态水对于生命（即碳基生命）至关重要。尽管可以设想在非常特定的物理环境中可能存在的其他化合物-溶剂对，但碳和水基生命所必需的元素是宇宙中最常见的元素。碳分子和液态水具有物理和化学性质，使它们成为优化的化合物-溶剂对。液态水对于重要的益生元反应至关重要。但对于生命的出现同样重要的是液态水中的碳分子与热岩石和矿物质的接触。我们在这里回顾了早期地球的环境条件，当时地球表面有液态水并且适合居住。我们将生命视为一种“宇宙现象”（de Duve 1995），即化学连续体，我们简要讨论了生命起源的各种假设，并指出它们与早期环境条件的相关性。看来热液环境在这方面很重要。我们继续记录早期生命，指出到了 3.5 Ga，当沉积环境开始得到良好保存时，厌氧生命形式已经殖民了从海底到暴露的海滩环境以及可能在海洋的透光浮游区的所有宜居微环境。地球上的生命也进化到了相对复杂的无氧光合作用阶段。最后，我们评估了太阳系其他行星和卫星的宜居性和殖民化潜力，指出太阳系甚至宇宙中最常见的生命形式与陆地化学营养生物相似，其碳源是还原碳或溶解在水中的二氧化碳，其能量来自氧化碳、H2或其他过渡元素。
Liquid water is essential for life as we know it, i.e. carbon-based life. Although other compound-solvent pairs that could exist in very specific physical environments could be envisaged, the elements essential to carbon and water-based life are among the most common in the universe. Carbon molecules and liquid water have physical and chemical properties that make them optimised compound-solvent pairs. Liquid water is essential for important prebiotic reactions. But equally important for the emergence of life is the contact of carbon molecules in liquid water with hot rocks and minerals. We here review the environmental conditions of the early Earth, as soon as it had liquid water at its surface and was habitable. Basing our approach to life as a “cosmic phenomenon” (de Duve 1995), i.e. a chemical continuum, we briefly address the various hypotheses for the origin of life, noting their relevance with respect to early environmental conditions. It appears that hydrothermal environments were important in this respect. We continue with the record of early life noting that, by 3.5 Ga, when the sedimentary environment started being well-preserved, anaerobic life forms had colonised all habitable microenvironments from the sea floor to exposed beach environments and, possibly, in the photic planktonic zone of the sea. Life on Earth had also evolved to the relatively sophisticated stage of anoxygenic photosynthesis. We conclude with an evaluation of the potential for habitability and colonisation of other planets and satellites in the Solar System, noting that the most common life forms in the Solar System and probably in the Universe would be similar to terrestrial chemotrophs whose carbon source is either reduced carbon or CO2dissolved in water and whose energy would be sourced from oxidized carbon, H2, or other transition elements.