Ares Vallis Cataract
The presence of this large cataract in Ares Vallis confirms that this channel was carved by water, probably in one or many large catastrophic flooding events.
The horseshoe-shaped headcut here is only part of a larger cataract system, and probably formed during the last stage of flooding. The inner channels are now filled with dunes formed by wind blowing along the channel floor.
@HiRISE Which way is the sun shining? From the right?