Abstract

Cryptic niches such as salt deposits are some of the last microbial refuges in many of the world’s deserts, including the Atacama—one of Earth’s oldest and driest deserts and a Mars analog for its hyperaridity, extensive salt deposits, severe diurnal temperature fluctuations and extremely high ultraviolet radiation. An NAI SETI 2016 pilot study revealed endolithic photosynthetic communities inhabit the gypsum domes of the Salar del Pajonales, including desiccation and radiation resistant cyanobacteria and heterotrophic bacteria. The current study’s objective was to map patterns in the spatial distribution and diversity of these photosynthetic communities. A total of 207 samples were examined. XRD detected predominantly gypsum for all habitats. Overall ~10% of non-polygon gypsum habitats were colonized and spatial patterns were patchy. Deflated gypsum ridges/domes, where crystals were exposed and evaporation was likely higher, were rarely colonized. Sandy, flat aeolian cover was more often colonized than intact domes/ridges. Aeolian cover and patterned ground polygons were inhabited by cyanobacterial soil crusts (BSC)—a rare mode of life near the Atacama’s hyperarid core. BSCs grew on compact gypsum or stable surfaces and colonized 100% of polygon edges vs 0% of polygon centers, suggesting colonization may be explained by porosity and water availability.