Gullies on Gorgonum Chaos mesas. This observation shows part of Gorgonum Chaos, a large cluster of chaotic terrain found in the Southern Hemisphere. Many regions of chaotic terrain are found at the head of large outflow channels that were scoured by ancient floods. Gorgonum Chaos is one region that is not associated with an outflow channel.
HiRISE Picture of the Day archive. [More at links]