Juncture of Two Branches of Dao Vallis (ctx frame - possible True Colors; credits: Lunar Explorer Italia)

Martian outflow channels are believed to be some of the largest features formed from the catastrophic flooding that scoured the landscape during ancient times. The source of the water likely originated in the subsurface and was somehow disturbed, depressurizing an aquifer, causing a sudden burst of water onto the surface.
This image shows multiple branches of the outflow channel Dao Vallis, which flows towards the West (down), ending near Hellas Basin. Although it is not clear exactly where the water that created these floods ended up, it is possible that Dao Vallis and its neighboring outflow channel, Niger Vallis, deposited water in Hellas Basin and formed a short-lived lake. Within the floor of Dao Vallis is material that appears striped, known as "lineated valley fill".
Valley fill material is thought to be ice-rich material that has flowed or been deposited onto the floor. Several lineations or "flow lines" appear to merge towards the upper left of the scene which supports this idea that the fill materials flowed, similar to slow-moving glacial material on Earth.

Also present in this scene is a mantling deposit which drapes much of the mid-latitudes of Mars. The deposit or "mantle" can be seen on south-facing slopes of positive-relief features, appearing as if its sliding off the walls. The mantle material is thought to be ice-cemented dust that was deposited during times when snowfall occurred on Mars.