At this location is an exceptionally long sinuous ridge, possibly an inverted fluvial feature, that cuts across newly mapped geologic units of the Medusae Fossae Formation.
In the eastern part of the image, the sinuous ridge appears in a manner that suggests erosion of the surrounding landscape. Interestingly, this fluvial feature has no elevation within and to the west location, indicating that fluvial activity may have occurred within this material before widespread erosion.
With HiRISE resolution, we might be able to have more information on the timing of fluvial activity and its relationship to the history of the Medusa Fossae formation.
Written by: HIRISE Science Team (audio by Tre Gibbs) (18 September 2013)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_032620_1780
Image: NASA/JPL/University of Arizona