Microbial geomorphologies in modern salt flats and their astrobiological significance

Following the discovery of Martian mineral deposits with an assumed evaporite origin (especially sulfates), salt flat areas from hot and cold arid environments (such as sabkhas and playa lakes) are currently investigated for comparative analysis between terrestrial salt-bearing settings and their Martian environmental analogs. Similarly to the Earth, evaporite deposits seem widespread on Mars where their stratigraphic setting and composition suggest relationships with aqueous environments and, therefore, they represent a useful indicator of habitability. Among the traces of biological activity retained in salt flat settings those produced by surface to near surface microbial activity deserve a special astrobiological interest. These microbial geomorphologies derive from the interaction between physical and biological agents, and can impact on the development and stabilization of surface morphologies with some fossilization potential. Therefore, once established a clear relationship between micro-geomorphologies and micro-biota, their recognition at the surface on Martian terrains may represent unambiguous indicators of biogenicity. In the sabkha Oum Dba, near the Atlantic coast of the Western Sahara (southern Morocco), thick microbial mats and mineral precipitations (carbonates and sulfates) are in progress and actively interact in an ecosystem where living and fossilized sectors coexist. It, therefore, represents an ideal natural site for detecting type, evolution, and stabilization of microbial geomorphologies in a typical arid salt flat area.