Abstract EANA2026-120

Sulfate evaporites are among the last hydrated minerals to form during progressive surface desiccation and are therefore key archives of late-stage aqueous activity, brine evolution, and potential habitability on Mars. However, the capacity of sulfate-rich deposits to retain biosignatures through repeated wet–dry cycling, cementation, and prolonged exposure to extreme surface conditions remains insufficiently constrained.

Modern gypsum microbialites from the Nuomuhong region of the Qaidam Basin, northern Tibetan Plateau, provide a cold, hyper-arid Mars analogue for investigating biosignature preservation in sulfate-rich deposits shaped by saline, iron-rich spring waters and strong seasonal evaporation. The microbialites form nodular, branched gypsum fabrics around a shallow perennial spring within an endorheic basin, providing a terrestrial analogue for sulfate precipitation in fluctuating brine systems.

An integrated analytical framework combines optical and scanning electron microscopy, X-ray diffraction, Raman spectroscopy, micro-computed tomography, drone-based contextual imaging, total organic carbon analysis, and evaporation modelling to link mineral fabrics, pore architectures, and microbe–mineral associations across scales. XRD and Raman analyses show gypsum-dominated mineralogy with minor carbonates and iron oxides, including hematite. Bulk organic carbon contents are low but reproducible, averaging ~0.20 wt% Corg, with no nitrogen detected, indicating sparse or strongly mineral-associated organic matter. Microscopy reveals laminated fabrics, diatom frustules, and putative microbial microtextures, while μCT imaging shows that pore networks remain partly connected despite extensive gypsum cementation. Smooth, rounded voids within the gypsum fabric are consistent with gas entrapment in cohesive microbial or EPS-rich substrates, suggesting that microbial activity may have influenced the development of internal pore architectures.

Ongoing work will extend this framework using Mars-mission-analogue instrumentation, including measurements with MOMA and an RLS twin instrument. These analyses will test how low-abundance organic matter, mineral-associated biosignatures, and sulfate-hosted textural features are detected under analytical configurations relevant to ongoing and future Mars missions.

Together, these results suggest that gypsum microbialites can preserve coupled records of brine evolution, microenvironmental habitability, and biosignature stabilization, even where bulk organic contents are low. They support sulfate-rich evaporitic deposits as high-priority targets for astrobiological exploration of Mars, while highlighting the need to evaluate biosignature detectability using mission-relevant analytical platforms.