Contributing Tributaries

I'm fascinated by geology, especially when seen from above. Pictures from the Mars Reconnaissance Orbiter are a favorite, and I particularly like images of gullies in crater walls; something is flowing down them, though it's not known just what. It could be water that flash melts for some reasons, but it could also be a form of carbon dioxide clathrates, which are still quite interesting but lack the oomph that water elicits in us. Anyway, here is a shot I quite like that was just taken, showing...