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Paleo-Rock-Hosted Life on Earth and the Search on Mars: a Review and Strategy for Exploration

Onstott, T. C. and Ehlmann, B. L. and Sapers, H. and Coleman, M. and Ivarsson, M. and Marlow, J. J. and Neubeck, A. and Niles, P. (2018) Paleo-Rock-Hosted Life on Earth and the Search on Mars: a Review and Strategy for Exploration. . (Unpublished)

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We review the abundance and diversity of terrestrial rock hosted life, the environments it inhabits, the evolution of its metabolisms, and its fossil biomarkers to provide guidance in the search for the biomarkers of rock hosted life on Mars. Key finds are metabolic pathways for chemolithotrophic microorganisms evolved much earlier in Earth history than those of surface dwelling phototrophic microorganisms,the emergence of the former occurred at a time when Mars was habitable, whereas that of the latter occurred at a time when the martian surface would have been uninhabitable, subsurface biomass do not correlate with organic carbon and tends to be highest at interfaces where chemical redox gradients are most pronounced, deep subsurface metabolic activity does not rely upon the respiration of organic photosynthate but upon the flux of inorganic energy and the abiotic and biotic recycling of metabolic waste products, and the rock record reveals examples of subsurface life back to 3.45 Ga with several examples of good preservation potential in rock types that are quite different from those preserving the photospheric supported biosphere.These findings suggest that rock hosted life would have likely to emerge and be preserved in a martian context. We thus propose a Mars exploration strategy that scales spatially, focusing initially on identifying rocks with evidence for groundwater flow and low temperature mineralization, then identifying redox and permeability interfaces preserved within rock outcrops, and finally focusing on finding minerals associated with redox reactions and traces of carbon and diagnostic biosignatures. The lessons from Earth show that ancient rock hosted life is preserved in the fossil record and confirmable via a suite of morphologic, organic, mineralogical and isotopic fingerprints and microscopic textures.

Item Type:Report or Paper (Discussion Paper)
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Ehlmann, B. L.0000-0002-2745-3240
Additional Information:This work has greatly benefited from the discussions and intellectual contributions of the 20 participants in the Rock Hosted Life Workshop February 8-10, 2017 at Caltech as well as the participants in the 4 pre-workshop telecons open to the community. Thanks to Mary Voytek and Michael Meyer at NASA Headquarters for workshop funding and to Penny Boston and the NASA Ames Research Center meeting support team for providing web-hosting for the telecons and their recording; all the information can be found at: We thank partial support of TCO through a subcontract supported by NASA Exobiology Award NASA NNX17AK87G to Andrew Schuerger of the University of Florida. The contribution of MC was carried out partly at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA), and via Grant NNA13AA94A issued through the NASA Science Mission Directorate and supported by the NASA Astrobiology Institute. No competing financial interests exist.
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Record Number:CaltechAUTHORS:20190402-084817695
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94356
Deposited By: Tony Diaz
Deposited On:02 Apr 2019 17:14
Last Modified:03 Oct 2019 21:03

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