Pre-global surveyor evidence for Martian ground water.

A time-dependent theory for the evolution of water on Mars is presented. Using this theory and invoking a large number of observational constraints, I argue that these constraints require that a large reservoir of water exists in the Martian crust at depths shallow enough to interact strongly with the atmosphere. The constraints include the abundance of atmospheric water vapor, escape fluxes of hydrogen and deuterium, D/H ratios in the atmosphere and in hydrous minerals found in one Martian meteorite, alteration of minerals in other meteorites, and fluvial features on the Martian surface. These results are consonant with visual evidence for recent groundwater seepage obtained by the Mars Global Surveyor satellite.