School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK.
UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK.
Bioessays. 2019 Aug;41(8):e1900052. doi: 10.1002/bies.201900052. Epub 2019 Jun 26.
Diverse micro-organisms populate a global deep biosphere hosted by rocks and sediments beneath land and sea, containing more biomass than any other biome except forests. This paper reviews an emerging palaeobiological archive of these dark habitats: microfossils preserved in ancient pores and fractures in the crust. This archive, seemingly dominated by mineralized filaments (although rods and coccoids are also reported), is presently far too sparsely sampled and poorly understood to reveal trends in the abundance, distribution, or diversity of deep life through time. New research is called for to establish the nature and extent of the fossil record of Earth's deep biosphere by combining systematic exploration, rigorous microanalysis, and experimental studies of both microbial preservation and the formation of abiotic pseudofossils within the crust. It is concluded that the fossil record of Earth's largest microbial habitat may still have much to tell us about the history of life, the evolution of biogeochemical cycles, and the search for life on Mars.
多样的微生物栖息于陆地和海洋之下的岩石和沉积物中，构成了一个全球性的深部生物圈，其生物量比除森林外的任何其他生物群落都多。本文综述了这些黑暗栖息地中一个新兴的古生物学档案：保存在地壳古老孔隙和裂缝中的微化石。这个档案，表面上似乎以矿化丝状体为主（尽管也有报道称存在棒状和球形微生物），但目前采样过于稀疏，且了解甚少，无法揭示深部生命随时间的丰度、分布或多样性的变化趋势。需要开展新的研究，通过系统探索、严格的微观分析以及对微生物保存和地壳中非生物假化石形成的实验研究，来确定地球深部生物圈化石记录的性质和范围。研究结论认为，地球最大微生物栖息地的化石记录可能还有很多关于生命历史、生物地球化学循环演化以及火星生命探索的信息有待我们去了解。
