Channels and ripples along crater walls. From the science rationale: “We would like a HiRISE image of the selected area to look for evidence of both fluvial and aeolian processes on the crater wall. Specifically, we are looking for channels that would be evident of erosion. It would be useful to know how widespread fluvial processes are across the surface of Mars and the timescale on which these processes take place.”
Beautiful Mars series. [More at links]