Seasonally Dependent Formation of Sulfates in the Basque Lakes, British Columbia, as Analogous to “Cold and Wet” and “Warm and Wet” Mars

Abstract Saline lakes are expected to have been extensively present on ancient Mars, particularly as the planet dried or cooled. Such lakes likely deposited sulfate salts, as these salts have been widely identified from orbital and in situ Mars data. However, the relationship between martian sulfates and the environmental conditions that formed them (including whether conditions were warm, cool, drying, or freezing), remains under‐characterized. To evaluate the relationship between sulfates and climate, we investigated the hypersaline, sulfate‐bearing Basque Lakes in British Columbia, Canada, which serve as an analog for both “cold and wet” and “warm and wet” early Mars. We use the rover and orbiter relevant instrument techniques of Raman, Near Infrared, and X‐Ray Fluorescence spectroscopy to evaluate seasonal lake mineralogy. We find that temperature‐dependent, multi‐cation salts form widely within the Basque Lakes' efflorescent crusts in the fall, which transform to meridianiite, mirabilite, a metastable Na‐sulfate 7‐hydrate, and epsomite in the wintertime. In both seasons, salt assemblages are metastable and persist beyond expected thermodynamic stability fields, suggesting ongoing climatic changes can prevent saline systems from settling into equilibrium phases. Coupled with sedimentological evidence, intimately mixed Mg‐sulfates of different hydration states could be an indicator of surface fluids that interacted with an atmosphere, while formation of Na‐sulfates could be evidence for brine freezing. Curiosity's exploration of the Gale crater sulfate‐bearing unit and Perseverance's exploration of Jezero crater on Mars offer excellent chances to investigate the influence of climate on Mg‐sulfate formation.