The positive detection of large hydrated sulfate deposits on the surface on Mars by the OMEGA instrument onboard Mars Express, the CRISM instrument onboard the Mars Reconnaissance Orbiter, as well as by in-situ excavation by the Mars Exploration Rovers motivates examination of the role of salts in the evolution of Martian topography and its potential habitability. The ability of salts to deform viscously under moderate stress and temperature regime lead to distinct geomorphic signatures in salt-rich terrain, such as collapse, lateral spreading, glacier-like flow, and diapirs. Such processes have been proposed recently to help explain terrain on Mars, such as the Thaumasia highlands, Valles Marineris, wrinkle ridges of the Thaumasia plateau, and the Juventae, Echus and Coprates outflow channels. Furthermore, the propensity of hydrated salts to dewater in the presence of heat could present opportunities for microbial life to be sustained in the resulting brines. Even if this heat was not sustained, evidence for past biological activity is preserved in gypsum and halite crystals on Earth, and thus potentially could be preserved on Mars. In this paper, a fresh comparative planetology discussion is presented, illustrated with terrestrial examples of salt-related landforms found around the world. In addition, we review studies of cold-loving (halophilic and psychrophilic) bacteria and archaea in Arctic brines, and discuss implications for habitability and preservation of microbial life.
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