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Published July 2020 | Published + Supplemental Material
Journal Article Open

Lipid Biomarker Record of the Serpentinite-Hosted Ecosystem of the Samail Ophiolite, Oman and Implications for the Search for Biosignatures on Mars

Abstract

Serpentinization is a weathering process in which ultramafic rocks react with water, generating a range of products, including serpentine and other minerals, in addition to H₂ and low-molecular-weight hydrocarbons that are capable of sustaining microbial life. Lipid biomarker analyses of serpentinite-hosted ecosystems hold promise as tools for investigating microbial activity in ancient Earth environments and other terrestrial planets such as Mars because lipids have the potential for longer term preservation relative to DNA, proteins, and other more labile organic molecules. Here, we report the first lipid biomarker record of microbial activity in the mantle section of the Samail Ophiolite, in the Sultanate of Oman, a site undergoing active serpentinization. We detected isoprenoidal (archaeal) and branched (bacterial) glycerol dialkyl glycerol tetraether (GDGT) lipids, including those with 0–3 cyclopentane moieties, and crenarchaeol, an isoprenoidal GDGT containing four cyclopentane and one cyclohexane moieties, as well as monoether lipids and fatty acids indicative of sulfate-reducing bacteria. Comparison of our geochemical data and 16S rRNA data from the Samail Ophiolite with those from other serpentinite-hosted sites identifies the existence of a common core serpentinization microbiome. In light of these findings, we also discuss the preservation potential of serpentinite lipid biomarker assemblages on Earth and Mars. Continuing investigations of the Samail Ophiolite and other terrestrial analogues will enhance our understanding of microbial habitability and diversity in serpentinite-hosted environments on Earth and elsewhere in the Solar System.

Additional Information

© 2020 Mary Ann Liebert, Inc. Submitted 12 March 2019; Accepted 4 February 2020; Published Online: 8 Jul 2020. The authors acknowledge the members of the Summons laboratory (MIT), and they thank Evelyn Mervine (the De Beers Group of Companies) for her assistance in sample collection and Charles Settens (MIT CMSE) for his help with XRD analyses. S.A.N. thanks Andrew Whitehill (EPA), Bethany Elhmann, and James Dickson (Caltech) for helpful conversations. They also thank two anonymous reviewers and Astrobiology Editor In Chief, S.L. Cady for their helpful comments and suggestions. No competing financial interests exist. Work by Kelemen, Mervine, and Shock was funded in part by NSF Research Grants EAR-1516300 and EAR-1049905, NASA grants 10-EXO10-0138 and 10-MFRP10-0098, and support from the International Continental Scientific Drilling Program and the Alfred P. Sloan Foundation. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation under award number DMR–1419807. S.O'R. acknowledges funding from Irish Research Council International Career Development Fellowships in Science, Engineering, and Technology—Cofunded by the European Commission Marie Curie Actions Programme (Grant No. 291760). This work was also supported by awards from the NASA Astrobiology Institute (award NNA13AA90A) and the Simons Collaboration on the Origins of Life (award #290361).

Attached Files

Published - ast.2019.2066.pdf

Supplemental Material - Supp-FigS1.pdf

Supplemental Material - Supp-FigS2.pdf

Supplemental Material - Supp-FigS3.pdf

Supplemental Material - Supp-TableS1.pdf

Supplemental Material - Supp-TableS2.pdf

Supplemental Material - Supp-TableS3.pdf

Supplemental Material - Supp-TableS4.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 20, 2023