'Hourglass' Shaped Craters Filled Traces Of Glacier

An hour-glass shaped feature is located in Promethei Terra, at the eastern rim of the Hellas Basin. It is believed to be the remnant of a block glacier with small amounts of rock that flowed from the feature into a nearby crater, which has since been filled. The glacier then flowed into a lower impact crater. End moraine-like features are seen in widening arcs at the site, with flow direction shown by middle-moraines. Ice is not stable at these latitudes for long periods of time, and therefore it can be inferred that glaciers must have formed here until a few million years ago. Noting the geologic features left behind by these glaciers can inform us where 'fossil' ice or evidence of water may be found currently on Mars.

http://www.sciencedaily.com/releases/2005/03/050325234724.htm