Aganippe Fossa

Aganippe Fossa is a fossa (surface feature) on Mars in the Phoenicis Lacus quadrangle. It is a graben that stretches around 600 km.

History
It is named after a classical albedo feature. It was first spotted in 1930, and officially named in 1976.

Description
Aganippe Fossa runs from 4.1° to 13° south latitude and 124.9° to 126.9° west longitude. It is one of the many dark slope streaks that are common on Mars. They occur on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter as they age. Sometimes they start in a tiny spot, then spread out and go for hundreds of meters. They have been seen to travel around obstacles, like boulders. It is believed that they are avalanches of bright dust that expose a darker underlying layer. However, several ideas have been advanced to explain them. Some involve water or even the growth of organisms. The streaks appear in areas covered with dust. Much of the Martian surface is covered with dust. Fine dust settles out of the atmosphere covering everything.