A newly released image from ESA’s Mars Express orbiter shows that catastrophic flooding — caused by ice melted from volcanic activity — created the Mangala Valles channels on Mars.
The perspective image on the right shows the topography of the region, with low points indicated in blue and high points by red. The channel along the right side of the image is Mangala Valles itself, though you can also see additional flood channels to the left of it passing around and through a large crater whose floor now stands above the surrounding terrain caused by the erosion of the rim plus the deposit of sediment inside the crater during the flooding.
I have a soft spot for Mangala Valles. When it was first photographed by the first orbiter missions to Mars in the early 1970s I was struck by its river-like appearance and striking topography. I therefore placed my Martian colony here in one of my efforts at science fiction writing. I figured it a good location for colonization, as there would likely be water and, by roofing over the deep canyon, a colony could be built relatively easily.
Better locations on Mars have since been found, but the location still intrigues me.