Open AccessInteractions Between Iron Sulfide Minerals and Organic Carbon: Implications for Biosignature Preservation and Detection
Author(s) -
Aude Picard,
Amy Gartman,
Peter R. Girguis
Publication year - 2021
Publication title -
astrobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.234
H-Index - 90
eISSN - 1531-1074
pISSN - 1557-8070
DOI - 10.1089/ast.2020.2276
Subject(s) - chemistry , iron sulfide , mineral , sulfide minerals , carbon fibers , organic matter , sulfide , chemical engineering , inorganic chemistry , organic chemistry , materials science , sulfur , composite number , engineering , composite material
Microbe-mineral interactions can produce unique composite materials, which can preserve biosignatures. Geological evidence suggests that iron sulfide (Fe-S) minerals are abundant in the subsurface of Mars. On Earth, the formation of Fe-S minerals is driven by sulfate-reducing microorganisms (SRM) that produce reactive sulfide. Moreover, SRM metabolites, as well as intact cells, can influence the morphology, particle size, aggregation, and composition of biogenic Fe-S minerals. In this work, we evaluated how simple and complex organic molecules-hexoses and amino acid/peptide mixtures, respectively-influence the formation of Fe-S minerals (simulated prebiotic conditions), and whether the observed patterns mimic the biological influence of SRM. To this end, organo-mineral aggregates were characterized with X-ray diffraction, scanning electron microscopy, and scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy. Overall, Fe-S minerals were found to have a strong affinity for proteinaceous organic matter. Fe-S minerals precipitated at simulated prebiotic conditions yielded organic carbon distributions that were more homogeneous than treatments with whole SRM cells. In prebiotic experiments, spectroscopy detected potential organic transformations during Fe-S mineral formation, including conversion of hexoses to sugar acids and polymerization of amino acids/peptides into larger peptides/proteins. In addition, prebiotic mineral-carbon assemblages produced nanometer-scaled filamentous aggregated morphologies. On the contrary, in biotic treatments with cells, organic carbon in minerals displayed a more heterogeneous distribution. Notably, "hot spots" of organic carbon and oxygen-containing functional groups, with the size, shape, and composition of microbial cells, were preserved in mineral aggregates. We propose a list of characteristics that could be used to help distinguish biogenic from prebiotic/abiotic Fe-S minerals and help refine the search of extant or extinct microbial life in the martian subsurface.