Dam like structures
In this rare color image taken by MSSS with the Mars Orbital Camera there appears to be dams which would collect water from the ravines. A shows one dam shape collecting water from the ravines above. B shows a second dam. C shows a third dam. D shows the edge between C and there is a fifth dam between this and E. F shows there is a high lip at the edge of the dams, and G shows the straight edge of this dam where it meets the crater wall. H shows another dam.
These may or may not be artificial, but there are a lot of them in only one area, near Cydonia.