Physical and chemical controls on habitats for life in the deep subsurface beneath continents and ice.
Physical and chemical controls on habitats for life in the deep subsurface beneath continents and ice.
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DOI：
10.1098/rsta.2014.0293
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发表时间：
2016-01-28
期刊：
影响因子：
--
通讯作者：
McMahon S
中科院分区：
文献类型：
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作者：
Parnell J;McMahon S
大陆地下生命的分布可能受到一系列物理和化学因素的控制。基本要求是生存空间、生物质碳和代谢活动能量。这些是相互关联的，因此需要足够的渗透性来维持养分的供应，并且相界面通过将多孔生境与营养丰富的泥岩并置而引发殖民化。存活的群落延伸至数公里深度，并随着孔隙度的减小而向下减小。碳是由最初通过光合作用固定的有机物的循环利用以及利用地壳二氧化碳和甲烷的化能自养提供的。在浅层地壳中，回收成分占主导地位，如加工过的干酪根或碳氢化合物，但非生物碳源在更深的变质地壳中可能很重要。氢可通过辐射分解、机械变形和矿物蚀变来化学合成燃料。次大陆深层生物圈的活动可以通过地质记录追溯到前寒武纪。在陆地植物殖民地球表面（地质学上最近发生的事件）之前，地下生命可能主导了地球的生物量。在厚冰盖区域，冰盖底部液态水稳定，并且由冰川侵蚀形成沉积层，可被视为深层生物圈栖息地。这种环境可能富含溶解的有机碳和因冰溶解、基岩和沉积层风化而积累的营养物质。
The distribution of life in the continental subsurface is likely controlled by a range of physical and chemical factors. The fundamental requirements are for space to live, carbon for biomass and energy for metabolic activity. These are inter-related, such that adequate permeability is required to maintain a supply of nutrients, and facies interfaces invite colonization by juxtaposing porous habitats with nutrient-rich mudrocks. Viable communities extend to several kilometres depth, diminishing downwards with decreasing porosity. Carbon is contributed by recycling of organic matter originally fixed by photosynthesis, and chemoautotrophy using crustal carbon dioxide and methane. In the shallow crust, the recycled component predominates, as processed kerogen or hydrocarbons, but abiotic carbon sources may be significant in deeper, metamorphosed crust. Hydrogen to fuel chemosynthesis is available from radiolysis, mechanical deformation and mineral alteration. Activity in the subcontinental deep biosphere can be traced through the geological record back to the Precambrian. Before the colonization of the Earth's surface by land plants, a geologically recent event, subsurface life probably dominated the planet's biomass. In regions of thick ice sheets the base of the ice sheet, where liquid water is stable and a sediment layer is created by glacial erosion, can be regarded as a deep biosphere habitat. This environment may be rich in dissolved organic carbon and nutrients accumulated from dissolving ice, and from weathering of the bedrock and the sediment layer.