Volatile history of Mangala Valles, Mars

Abstract

Mangala Valles are unique among Martian outflow channels because they emanate from a point source determined by the interaction of tectonism, volcanism, and volatile migration. Present topography and morphology place constraints on the magnitude of the discharge into the channels, supporting a release of water which spanned from tens to thousands of days. The sequence of events associated with the release of volatiles in the southern (proximal) reaches of Mangala Valles indicates that structural features around the source area played a crucial role in determining the location of the apparent source of volatile release onto the Martian surface. Postulated locations for storage of the water released into the Mangala Valles system include aquifer systems in the highlands south of the release point, within the layered flows of the Tharsis plains, and a surface lake in the Daedalia Planum area. Hydraulic conductivity within the aquifer could have inhibited a sudden release of all the stored water, lengthening the total discharge duration toward the longer time frame indicated above. Topographic and structural constraints favor groundwater flow from the Tharsis region, which may have manifested itself at the Mangala source area as an artesian flow. Fluid release into the Mangala Valles system likely included sheet flows and episodic surges of water resulting from temporary ice dams within the channel system and may have included releases from more than a single location.