Mangala Valles, located in tropical regions of Mars, is interpreted to have formed by dike-induced cracking of the cryosphere to produce a linear graben and catastrophic release of groundwater sequestered under hydrostatic pressure. Outpouring of water and downcutting led to erosion and widening of the graben to produce a trough. Patterns of ridges and lobes along the outer rims of the trough are interpreted to have formed primarily by local accumulations of snow and ice on the graben rim (derived from exposed ponded groundwater in the graben), and glacial-like outward flow of ice lobes resulting in development of moraines and tills along the north and south rims of the trough. These observations and interpretations support the concept that the climate of Mars was a hyper-arid cold polar-like desert similar to today in the Late Hesperian-Early Amazonian period.