CaSO4 crust as potential habitat for microbial life in the extreme hyperarid Atacama Desert and their reciprocal effects

The Atacama Desert is one of the most extreme landscapes and environments on Earth. Due to its predominant hyperarid climate and high UV radiation, life is mostly absent. Prolonged aridity causes the formation of CaSO4-rich soils and crusts from mostly atmospheric deposition and aeolian input, creating a blanket covering vast landscapes. Water as the defining pre-requisite for life is scarce, however, infrequent precipitation events, fog and dew are potential moisture sources. CaSO4-rich soils in the Atacama Desert are cemented due to secondary modification (dissolution, transport and re-precipitation) of CaSO4 minerals (Gypsum-Basanite-Anhydrite) and other soluble salts, which form an indurated surface cover with several dm to meters thickness. Within these CaSO4-rich soils, cavities and cracks are partly covered with recrystallized evaporitic minerals indicating the temporal presence of water activity (of unknown state and volume). Harsh environmental conditions on the surface contrast life in the subsurface. Microbial communities from different groups of bacteria, archaea and eukaryotes inhabit such endolithic environments, living from captured moisture within the soil, or potential from hydrated CaSO4. Their presence and interaction, however, can also influence pedogenic processes, contributing to CaSO4 dynamics as landscape forming agent and as preconditions for higher developed life. We present some initial results from a CaSO4-rich soil crust study from the Atacama Desert, using XRD, ICP-OES, and SEM imaging along with the lipid-biomarker analysis to explore and characterize the CaSO4-rich soil as habitat for microbial life, and to unravel the potential impact of microbial life on landscape forming processes, i.e. CaSO4 soil dynamics.