Abstract
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 ∑CO2. 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.This article is part of a discussion meeting issue ‘Serpentinite in the Earth System’.
Highlights
Serpentinites are formed when ultramafic rocks, like those in Earth’s mantle, are exposed to water
High concentrations of H2 and appropriate catalysts in a hydrothermal system can lead to the abiotic synthesis of organic molecules, which provide a source of food for life and could have played a major role in early biochemical evolution [1,2]
If it can be shown that serpentinization supports self-sustaining ecosystems, independent of sunlight and independent of magmatic activity, the diversity of habitats and planets potentially capable of supporting ecosystems would be expanded even further to include any habitat that has serpentinizing rock and liquid water. It remains unclear whether serpentinization and its associated geochemical reactions are sufficient to support the origin and evolution of life independently of other geological processes, or if the products of serpentinization must be mixed with other materials to meet all of the requirements for continuous habitability [7]
Summary
Serpentinites are formed when ultramafic rocks, like those in Earth’s mantle, are exposed to water. The discovery of chemoautotrophic ecosystems in seafloor hydrothermal systems in the 1970–80s revealed that magmatic energy from the Earth’s deep interior can support robust, self-sustaining ecosystems, independently of the organic remains from photosynthesis This discovery dramatically expanded the potential possibilities for life outside Earth to include potential habitats that are magmatically active even if they lack abundant sunlight. If it can be shown that serpentinization supports self-sustaining ecosystems, independent of sunlight and independent of magmatic activity, the diversity of habitats and planets potentially capable of supporting ecosystems would be expanded even further to include any habitat that has serpentinizing rock and liquid water It remains unclear whether serpentinization and its associated geochemical reactions are sufficient to support the origin and evolution of life independently of other geological processes, or if the products of serpentinization must be mixed with other materials to meet all of the requirements for continuous habitability [7]. We use research results from expeditions to the Lost City and the Atlantis Massif as our bases for assessing habitability of the oceanic serpentinite subsurface
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