22-EPN3-30: An Isotopic Inventory of Mars Analogue Environments
Visit by Michael Christopher Macey of the Open University (UK), to TA2 Facility 17 – Isotoptech Stable/Clumped Isotopes Laboratory (Hungary).
Dates of visit: 06-10 November 2023.
Report Summary: This study analysed the carbon, oxygen, sulfur, and nitrogen isotope profiles in physiochemically distinct analogue environments to establish how the viability of biologically induced isotope fractionation as a candidate biosignature. The analysis was performed on sediment samples collected from analogue environments proposed as appropriate analogues for Noachian-Hesperian waters requires environments (e.g., highly saline and sulfurous). Specifically, these environments were the Salt flats of Western Sahara, a hypersaline environment that contains sulfurous sediments below thick halite layers, the high-altitude lakes of the Argentinian Andes, which possess a chemistry like dilute, modelled martian water chemistries and are impacted by a low atmospheric pressure and large diurnal fluxes in temperature and UV, the salt pans of the Makadikadi basin, and hypersaline lakes in Spain.
The analysis identified varied isotopic signatures across locations suggestive of diverse environmental conditions in terms of their microbial community, geology and inputs to the environment. Key differences include: Positive 34S ad low 13C values in the Botswanan sediments, aligning with the detection of oxic conditions, while negative values in Argentinian and Saharan samples indicate a contribution of dissimilatory sulfur metabolisms. Variation in 15N values between environments highlight previously detected variation in the presence and abundance of nitrogen-dependent metabolisms. The 18O values also strongly support the input of glacial water into the Argentinian lakes. The synthesis of this isotopic analysis with geochemical and microbiological datasets from these Mars analogue environments stands to provide crucial insight into their role as potential biosignatures.
