Are Large Sulfur Isotope Variations Biosignatures in an Ancient, Impact-Induced Hydrothermal Mars Analog?

Discrepancies have emerged regarding the software of sulfur secure isotope ratios as a biosignature in impression crater paleolakes.

The primary in situ δ³⁴S knowledge from Mars at Gale crater show a ∼75‰ vary that has been attributed to an abiotic mechanism. But biogeochemical research of historic environments on Earth typically interpret δ³⁴S fractionations >21‰ as indicative of a organic origin, and research of δ³⁴S at analog impression crater lakes on Earth have adopted the identical strategy.

We carried out analyses (together with δ³⁴S, complete natural carbon wt%, and scanning electron microscope imaging) on a number of lithologies from the Nördlinger Ries impression crater, specializing in hydrothermally altered impression breccias and related sedimentary lake-fill sequences to find out whether or not the δ³⁴S properties outline a biosignature.

The variations in δ³⁴S between the host lithologies might have resulted from thermochemical sulfate discount, microbial sulfate discount, hydrothermal equilibrium fractionation, or any mixture thereof. Regardless of plentiful samples and instrumental precision at present unique to Earth-bound analyses, assertions of biogenicity from δ³⁴S variations >21‰ on the Miocene Ries impression crater are tenuous.

This discourages using δ³⁴S as a biosignature in related environments with out impartial checks that embrace the total geologic, biogeochemical, and textural context, in addition to a complete acknowledgment of other hypotheses.

Christopher J Tino, Eva E Stüeken, Gernot Arp , Michael Ernst Böttcher, Steven M Bates, Timothy W Lyons

https://pubmed.ncbi.nlm.nih.gov/37498995/
PMID: 37498995 DOI: 10.1089/ast.2022.0114

Astrobiology