Mangala Valles
The Mangala Valles are a complex system of criss-crossing channels on Mars, located in the Tharsis region and in the Memnonia quadrangle. They originated in the Hesperian and Amazonian epochs. They are thought to be an outflow channel system, carved by catastrophic floods, and the release of vast quantities of water across the Martian surface. This flooding was probably initiated by tectonic stretching and the formation of a graben, Mangala Fossa, at the channels' head, perhaps breaching a pressurized aquifer trapped beneath a thick "cryosphere" (layer of frozen ground) beneath the surface. The Mangala Valles contain several basins; after they filled, the overflow went through a series of spillways. One source of waters for the system was the Memonia Fossae, but water also probably came from a large basin centered at 40 degrees S. A recent study that used photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy, demonstrated that the Mangala Valles were flooded by water at least twice and covered with lava at least three times during the Late Amazonian. The presence of scoured bedrock at the base of the mapped stratigraphy, together with evidence from crater retention ages, suggests that fluvial activity came before lava flows.