Radiolytically reworked Archean organic matter in a habitable deep ancient high-temperature brine

Devan M Nisson; Clifford C Walters; Martha L Chacón-Patiño; Chad R Weisbrod; Thomas L Kieft; Barbara Sherwood Lollar; Oliver Warr; Julio Castillo; Scott M Perl; Errol D Cason; Barry M Freifeld; Tullis C Onstott

doi:10.1038/s41467-023-41900-8

Radiolytically reworked Archean organic matter in a habitable deep ancient high-temperature brine

Nat Commun. 2023 Oct 3;14(1):6163. doi: 10.1038/s41467-023-41900-8.

Authors

Affiliations

¹ Department of Geosciences, Princeton University, Princeton, NJ, 08540, USA. dnisson@princeton.edu.
² Bureau of Economic Geology, University of Texas, Austin, TX, 78758, USA.
³ National High Magnetic Field Laboratory, Tallahassee, FL, 32310, USA.
⁴ Department of Biology, New Mexico Institute of Mining and Technology, Socorro, NM, 87801, USA.
⁵ Department of Earth Sciences, University of Toronto, Toronto, ON, M5S 3B1, Canada.
⁶ Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, 1 rue Jussieu, 75005, Paris, France.
⁷ Department of Earth Sciences, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
⁸ Department of Microbiology and Biochemistry, University of the Free State, Bloemfontein, 9300, South Africa.
⁹ NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA.
¹⁰ Department of Animal Sciences, University of the Free State, Bloemfontein, 9300, South Africa.
¹¹ Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹² Department of Geosciences, Princeton University, Princeton, NJ, 08540, USA.

Abstract

Investigations of abiotic and biotic contributions to dissolved organic carbon (DOC) are required to constrain microbial habitability in continental subsurface fluids. Here we investigate a large (101-283 mg C/L) DOC pool in an ancient (>1Ga), high temperature (45-55 °C), low biomass (10²-10⁴ cells/mL), and deep (3.2 km) brine from an uranium-enriched South African gold mine. Excitation-emission matrices (EEMs), negative electrospray ionization (-ESI) 21 tesla Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and amino acid analyses suggest the brine DOC is primarily radiolytically oxidized kerogen-rich shales or reefs, methane and ethane, with trace amounts of C₃-C₆ hydrocarbons and organic sulfides. δ²H and δ¹³C of C₁-C₃ hydrocarbons are consistent with abiotic origins. These findings suggest water-rock processes control redox and C cycling, helping support a meagre, slow biosphere over geologic time. A radiolytic-driven, habitable brine may signal similar settings are good targets in the search for life beyond Earth.

Grants and funding

EAR2026853/National Science Foundation (NSF)