Valles Marineris, Mars. Artwork of Valles Marineris canyon system as the Sun sets. It is found on Mars, the fourth planet in our Solar System. The Valles Marineris is over 4000 kilometres (km) long, up to 200 km wide and up to 7 km deep, dwarfing the Grand Canyon of Arizona, USA. The canyons are found on the southeastern edge of the Tharsis Bulge and were originally created by faulting during the formation of Tharsis. The canyons have been further worn down by water and wind erosion. Finally, slumping has helped widen the canyon so that the bottom is visible from space.