CHARACTERIZING BIOTIC AND ABIOTIC MG CARBONATE MINERAL FORMATION IN POTENTIAL MARS ANALOGUE ENVIRONMENTS: ALKALINE LAKES AND PLAYAS OF BRITISH COLUMBIA

The highly alkaline, sometimes hypersaline, lake and playa systems in British Columbia have been recognized as potential analogues to the Mars Jezero crater paleolake due to their production of magnesium (Mg) carbonate minerals within underlying and surrounding ultramafic bedrock basins. Within these systems, Mg carbonate minerals form within microbial mats lining the edges of the lakes, on the shoreline as microbial “mounds”, and abiotically via carbonation of serpentinite. However, we lack a diagnostic set of textural, geochemical, and isotopic characteristics that can distinguish the biotically formed from the abiotically formed Mg carbonate minerals. Here, we survey Mg carbonate facies from Atlin playa and Cariboo Plateau lakes (British Columbia, Canada) from field to microscopic scale. Our goals in this survey are to (1) to connect microbiological processes to specific properties of the Mg carbonate minerals and differentiate them from abiotically formed Mg carbonate, and (2) to provide a toolkit to assess whether microbial life was involved—or not—in the precipitation of Mg carbonate minerals. We assessed enzyme activity of Carbonic Anhydrase in mats precipitating Mg carbonates by field assay. We also collected samples for 16s rRNA gene sequencing and fluorescently labelled embedded coring (FLEC) to both identify the microbial community composition and observe the spatial relationships among living cells and the carbonate textures commonly ascribed to life. We will present the findings of our field survey including the conditions in which these Mg carbonate producing microbial mats grow as well as the mineral phases we observed within the mats and mounds. We also present our hypothesized conceptual model for geochemical and petrographic analyses like dual-clumped isotope measurements (∆₄₇-∆₄₈), trace metal concentrations, and FLEC data based on our preliminary findings. The synthesis of data collected from these lakes/playas will provide a framework to evaluate the biogenicity of Mg carbonate minerals on Earth and potentially Mars.