Recent Water Release in the Tharsis Region of Mars

The anastomosing form and associated streamlined islands of the numerous channels identified in the northwestern Tharsis region of Mars indicate that they were probably formed by flowing water. An account is given of a channel-formation model for Tharsis which invokes the (most probable) action of the tectonic release of water from a deep groundwater system, or (less probably) the intrusive heating of deep-seated ice lenses. It is speculated, in view of the channels' occurrence in some of the youngest lava flows on Mars, that either water or ice may have existed in the equatorial latitudes of Mars until as recently as 1 billion years ago.