Dao and Niger Valles

Today's VIS image shows a small portion of both Dao Vallis (top of image) and Niger Vallis (middle of image). Arising from the volcano Hadriacus Mons, Dao Vallis is approximately 1200km (750 miles) long. Niger Vallis is 333 km (207 miles) long. It has been proposed that heating of the region due to volcanic activity melted subsurface ice which was released to the surface to carve the two channels. Niger Vallis merges with Dao Vallis just off the image and then flow southwestward into the Hellas Planitia basin.