Organic biosignature degradation in hydrothermal and serpentinizing environments: Implications for life detection on Icy Moons and Mars
File(s)
Accepted version
Author(s)
Tan, Jonathan
Salter, Tara
Watson, Jonathan
Waite, J Hunter
Sephton, Mark
Type
Journal Article
Abstract
Evidence of liquid water is a primary indicator of habitability on the icy moons in our outer solar system as well as on terrestrial planets such as Mars. If liquid water-containing environments host life, some of its organic remains can be fossilized and preserved as organic biosignatures. However, inorganic materials may also be present and water-assisted organic-inorganic reactions can transform the organic architecture of biological remains. Our understanding of the fate of these organic remains can be assisted by experimental simulations that monitor the chemical changes that occur in microbial organic matter due to the presence of water and minerals. We performed hydrothermal experiments between 100–300°C involving lipid-rich microbes and natural serpentinite mineral mixtures generated by the subaqueous hydrothermal alteration of ultramafic rock. The products reveal what the signals of life may look like when subjected to water-organic-inorganic reactions. Straight and branched chain lipids in unaltered samples are joined by cyclization and aromatization products in hydrothermally altered samples. Hydrothermal reactions produce distinct products that are not present in the starting materials including small, single-ring, heteroatomic and aromatic compounds such as indoles and phenols. Hydrothermal reactions in the presence of serpentinite minerals lead to the significant reduction of these organic structures and their replacement by diketopiperazines (DKPs) and dihydropyrazines (DHPs), which may be compounds that are distinct to organic-inorganic reactions. Given that the precursors of DKPs and DHPs are normally lost during early diagenesis, the presence of these compounds can be an indicator of co-existing recent life and hydrothermal processing. However, the thermal stability of these compounds reveals that the formation and preservation of these compounds only occurs within a distinct temperature window. Serpentinite is also found to have a preservative effect on some compounds, such as alkylamides. Our findings are relevant to life detection missions that aim to access hydrothermal and serpentinizing environments in the subsurfaces of icy moons and Mars.
Date Issued
2023-10-17
Date Acceptance
2023-07-02
Citation
Astrobiology, 2023, 10 (10), pp.1045-1055
ISSN
1531-1074
Publisher
Mary Ann Liebert
Start Page
1045
End Page
1055
Journal / Book Title
Astrobiology
Volume
10
Issue
10
Copyright Statement
© 2023, Mary Ann Liebert, Inc., publishers. For the purpose of Open Access, the author has applied a Creative Commons Attribution (CC-BY) licence to any Author Accepted Manuscript (AAM) version arising.
License URL
Publication Status
Published
Date Publish Online
2028-07-28