Imaging Current and Ancient Subsurface Water and Ice on Mars

A variety of satellite imagery is being applied to studies of the current and paleo-hydrogeology of the planet Mars. Gamma ray spectroscopy and radar sounding document extensive planetary-scale deposits of subsurface water ice. Visible and near-infrared imagery show evidence of very ancient outbursts of subsurface water, some of which generated megaflooding on early Mars that induced global climatic change. The University of Arizona’s High Resolution Imaging Science Experiment (HiRISE) has recently generated images showing ongoing seepage of what are probably brines on present-day Mars. It is now clear that Mars, like Earth, has had a dynamic hydrological cycle, operating on a planetary scale, over the entire history of the planet, and that this cycle involved complex interactions of both groundwater and surface water components interacting with an evolving atmosphere and cryosphere.