Valles Marineris is Mars’ largest canyon system The entire system extends over 4000 km (2490 mi), covering about one fifth the circumference of Mars. Some parts of the canyon run as deep as 7 km (4 mi) and as wide as 200 km (125 mi). Compared to Valles Marineris, the Grand Canyon on Earth seems quite small at 446 km (277 mi) long, 30 km (18 mi) wide and 1.6 km (1 mi) deep. If Valles Marineris was placed on the surface of Earth, it would stretch from Los Angeles to the Atlantic coast.