Dao Vallis

Dao Vallis is a valley on Mars that appears to have been carved by water. It runs southwestward into Hellas Planitia from the southern slopes of the volcano Hadriacus Mons, and has been identified as an outflow channel. It and its tributary, Niger Vallis, extend for about .
It is named after the Thai word for star, and it was proposed as a potential landing site for the 2012 Curiosity rover of the Mars Science Laboratory mission. In the fictional 2007 Canadian miniseries "Race to Mars", it is the landing site for "Gagarin", the lander.
Origin.
Dao Vallis begins near a large volcano, Hadriacus Mons, so it is thought to have received water when hot magma melted huge amounts of ice in the frozen ground. Much of this water may have been released in very large "outburst floods". The partially circular depressions on the left side of the channel in the image below suggests that groundwater sapping also contributed water more gradually.