This region of Mars has been long studied for its evidence of glacial-like flow features. The landscape is dominated by flat top mesas and flat valley floors. But a closer look shows evidence that soil material is flowing ever so gradually from the edges of the mesas out into the valleys.
Such flow can result from excessively ice-rich deposits analogous to glaciers. “Streamlines” (curved ridges) mark the flow direction, while “flow fronts” mark where material has reached its furthest extent or where material has collided with an obstacle or otherwise bunched up.
The close up view from HiRISE reveals even stranger textures on the valley floor. Scarps and hills appear twisted like taffy, probably the result of the slow movement of the subsurface ice. Other areas that appear flat and smooth at lower resolution are expanses of extremely regular small pits and mounds at HiRISE resolution. One suggestion has been that these small-scale textures are the result of sublimation (evaporation) of subsurface ice combined with the taffy-like shifts in the ground surface.
Written by: Mike Mellon (28 November 2012)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_028313_2220
Image: NASA/JPL/University of Arizona