Radiolytically reworked Archean organic matter in a habitable deep ancient high-temperature brine.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37789019.
- Also identified by DOI 10.1038/s41467-023-41900-8 and PMC identifier 10547683.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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 (10<sup>2</sup>-10<sup>4</sup> 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 C<sub>3</sub>-C<sub>6</sub> hydrocarbons and organic sulfides. δ<sup>2</sup>H and δ<sup>13</sup>C of C<sub>1</sub>-C<sub>3</sub> 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.