Saltpan sediment as a Mars analog

Brines at or near the surface of present-day Mars are a potential explanation for seasonally recurring dark streaks on the walls of craters, termed recurring slope lineae (RSL). Deliquescence and freezing point depression are possible drivers of brine stability, attributable to the high salinity observed in Martian regolith including chlorides and perchlorates. Investigation of life which may inhabit RSL, and the cellular mechanisms necessary for survival, must consider tolerance of highly variable hydration, freeze-thaw cycles, and high osmolarity in addition to the anaerobic, oligotrophic, and irradiated environment. We propose the saltpan, an ephemeral, hypersaline wetland as an analog for putative RSL hydrology. Saltpan sediment archaeal and bacterial communities showed tolerance of Mars-analogous atmosphere, hydration, minerology, salinity, and temperature. While active growth and a shift to well-adapted taxa were observed, susceptibility to low concentration chloride and perchlorate addition suggested such a composition was insufficient for protective water stability relative to added osmotic stress.