A new frontier for palaeobiology: Earth’s vast deep biosphere

Sean McMahon, Magnus Ivarsson

Research output: Contribution to journalArticlepeer-review


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. Here, we review an emerging palaeobiological archive of these dark habitats: microfossils preserved in ancient pores and fractures in the crust. This archive, seemingly dominated by mineralised 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. We call for new research 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. We conclude 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
Original languageEnglish
Early online date26 Jun 2019
Publication statusE-pub ahead of print - 26 Jun 2019


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