Habitability of the marine serpentinite subsurface: a case study of the Lost City hydrothermal field

Abstract

<jats:p> The Lost City hydrothermal field is a dramatic example of the biological potential of serpentinization. Microbial life is prevalent throughout the Lost City chimneys, powered by the hydrogen gas and organic molecules produced by serpentinization and its associated geochemical reactions. Microbial life in the serpentinite subsurface below the Lost City chimneys, however, is unlikely to be as dense or active. The marine serpentinite subsurface poses serious challenges for microbial activity, including low porosities, the combination of stressors of elevated temperature, high pH and a lack of bioavailable ∑CO <jats:sub>2</jats:sub> . A better understanding of the biological opportunities and challenges in serpentinizing systems would provide important insights into the total habitable volume of Earth's crust and for the potential of the origin and persistence of life in Earth's subsurface environments. Furthermore, the limitations to life in serpentinizing subsurface environments on Earth have significant implications for the habitability of subsurface environments on ocean worlds such as Europa and Enceladus. Here, we review the requirements and limitations of life in serpentinizing systems, informed by our research at the Lost City and the underwater mountain on which it resides, the Atlantis Massif. </jats:p> <jats:p>This article is part of a discussion meeting issue ‘Serpentinite in the Earth System’.</jats:p>

Subduction hides high-pressure sources of energy that may feed the deep subsurface biosphere

“…Additionally, H 2 , CO and NH 3 found to be abundant in the deep metamorphic fluids in this study might fuel widespread chemolithoautotrophy as recently reported at convergent margins 2,3 and other subsurface continental settings 87 . Heterotrophic and fermentative members of the community commonly reported in other continental settings 78,87 may be supported by the aqueous organic species resulting from abiotic synthesis (e.g., formate and acetate 88 ). Overall, the presence of a large supply of reduced volatile species has the potential to support diverse microbial assemblages at convergent margin.…”

Genomic Evidence for Formate Metabolism by Chloroflexi as the Key to Unlocking Deep Carbon in Lost City Microbial Ecosystems

“…Serpentinite-hosted systems are of astrobiological interest because they provide a source of energy for life that does not require sunlight or vigorous magmatic activity (1). These systems are thought to be present on icy worlds such as Jupiter's moon Europa and Saturn's moon Enceladus (2,3).…”

The ambivalent role of water at the origins of life

“…Modern serpentinising systems harbour temperature, pH and redox gradients [94] and provide carbon (mostly in the form of CO 2 /carbonates), sulphur (H 2 S and sulphide minerals), and in lesser or trace amounts also nitrogen and phosphate [137]. A unique feature of serpentinising systems is the continuous production of hydrogen (H 2 ) from water, providing the surroundings with a constant supply of electrons, a very low midpoint potential [138], and a chemical energy source [139–141].…”