Valles Marineris

This great rift canyon on Mars, seen here in a Viking mosaic image, has a length of 2400 miles (it would reach from Washington, DC to Los Angeles), a maximum width of 70 miles, and a maximum depth of 22,000 feet. It is vastly larger than the US „Grand“ Canyon, which would barely qualify as a „side channel“ here. Valles Marineris was not produced by water flow (although many smaller Martian channels were). Instead, it appears to have formed by a stretching and tearing of the Martian crust during the Tharsis plume upwelling event. Here is a video animation (9 MB) of a „flyover,“ based on Mars Odyssey images, which gives a good sense of the scale and structure of Valles Marineris.