The central portion of this image features a mildly-winding depression that was carved by water, likely around four billion years ago shortly after the Hellas basin formed following a giant asteroid or comet impact.
Water would have flowed from the uplands (to the east) and drained into the low-lying basin, carving river channels as it flowed. The gentle curves—called “meanders” by geomorphologists—imply that this paleoriver carried lots of sediment along with it, depositing it into Hellas.
Written by: Kirby Runyon (audio: Tre Gibbs) (15 July 2016)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_045611_1410
Image: NASA/JPL/University of Arizona