Arnus Vallis Layers, as seen by HiRISE. Scale bar is 500 meters long.
Arnus Vallis is an ancient river valley in the Syrtis Major quadrangle of Mars, located at 14.1° north latitude and 289.5° west longitude. It is 280 km long and was named after the classical and present day Arno River in Tuscany, Italy (previously named Arena Rupes).
Original source: https://en.wikipedia.org/wiki/Arnus Vallis. Read more