[Communications Earth & Environment] Understanding organic matter preservation in extreme environments is crucial for detecting potential biosignatures on Mars.
Although clay minerals and evaporites can each preserve organic matter individually, their synergistic preservation mechanisms remain an active area of investigation.
Here, we investigate the preservation of organic matter in ancient evaporite minerals from the Qaidam Basin, using integrated in situ microanalytical techniques to analyze solid/fluid inclusions within displacive gypsum and cumulate halite formed during the Middle Pleistocene.
Our analyses reveal well-preserved organic matter, including β-carotene and kerogen, adsorbed onto clay particles both in solid inclusions within gypsum and fluid inclusions within halite.
Geochemical data are consistent with a potential biogenic contribution, whereas metagenomic data from modern Qaidam soils provide ecological context rather than direct evidence for the origin of the preserved organic matter.
We propose a dual-mineral protection mechanism, wherein clay minerals initially adsorb organic compounds, which are subsequently encapsulated by growing salt crystals. This two-stage process leverages the complementary protective properties of both mineral types and enhances long-term organic preservation.
Our findings identify a specific mineral association capable of preserving Martian organic biosignatures and provide strategic guidance for selecting exploration targets in future Mars missions.
Optical and SEM images, Raman spectra, and NanoSIMS elemental maps of a solid inclusion within gypsum. The region outlined by the white dashed line corresponds to the same area across (A-G). (A) An optical image of a gypsum solid inclusion. (B-F) NanoSIMS elemental maps of the inclusion in (A), showing distribution of elements 12C (B), 12C 14N (C), 16O (D), 28Si (E) and 27Al16 194 O (F), respectively. The more intense the color, the stronger the response, with red being the strongest response in all cases. (G) A SEM image of the solid inclusion shown in (A). (H-I) Raman spectrum of the inclusion shown in (G), showing the D-band and G-band of kerogen and OH198 peaks of clay minerals. The table at the bottom of the figure presents the elemental compositions obtained from spot SEM–EDS analyses. The analytical locations are marked by the red circles in (G). — Communications Earth & Environment
A dual-mineral protection mechanism for organic matter preservation and its implications for Mars habitability and biosignature detection, Communications Earth & Environment
Astrobiology,
