Salt tectonics and collapse of Hebes Chasma, Valles Marineris, Mars

A photogeologic and physical modeling study indicates that Hebes Chasma, Mars, formed by collapse of the megaregolith. Local heating facilitated drainage of ~105 km3 of brines and entrained particulates through fractures in the chasma fl oor and into a regional aquifer. A megaregolith rich in salts and water is implied by massive, low-gradient allochthonous fl ows that terminate in deep pits and troughs, by emergent diapirs, and by arching of Hebes Mensa. These structures are consistent with plastic and viscous deformation but inconsistent with collapse of basalt fl ows and/or tephra. Spectral measurements confi rm that hydrated sulfate salts are spatially associated with allochthonous fl ows from depth and light-toned deposits. Collapse features and fl ows are present in many other chasmata in Valles Marineris, suggesting that widespread salt tectonics and dissolution may have shaped the region.