Illustration of an oblique view of the giant Valles Marineris canyon system on Mars. The Valles Marineris is over 3000 kilometres long and up to 8 kilometres deep, dwarfing the Grand Canyon of Arizona, USA. The canyons were formed by a combination of geological faulting, landslides, and erosion by wind and ancient water flows. The view is looking west, from an altitude of about 2000 kilometres, and shows the canyon filled with low-altitude fog and cloud.