Physical and Chemical Controls on Habitats for Life in the Deep Subsurface Beneath Continents and Ice

John Parnell, Sean Hendry McMahon

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26 Citations (Scopus)
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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.
Original languageEnglish
Article number20140293
JournalPhilosophical Transactions of the Royal Society of London. Series A
Issue number2059
Early online date14 Dec 2015
Publication statusPublished - Jan 2016

Bibliographical note

S.M. was funded by an STFC Aurora studentship (grant ST/1506102/1) and the NASA Astrobiology Institute Program on Foundations of Complex Life, Evolution, Preservation and Detection on Earth and Beyond (grant NNA13AA90A). J.P. was supported by NERC grant NE/G00322X/l.


  • deep biosphere
  • subglacial life
  • Antarctica
  • biogeochemistry
  • cell density


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