Measuring the length of the entire United States, Mars’ Valles Marineris—Mariner Valley—is an enormous canyon that makes our Grand Canyon appear minuscule. Stretching across a good expanse of the Red Planet, Valles Marineris is captured in spectacular detail thanks to the work of the Viking orbiter. NASA’s high-resolution mosaic of the Valles Marineris hemisphere gives a magnificent look at this canyon system.

Located along Mars’ equator, Valles Marineris spans one-fifth of the entire circumference of the planet. With depths of up to 4 miles and widths reaching up to 120 miles, the 2,500-mile-long canyon system is one of the largest in the entire Solar System. To put things into perspective, the Grand Canyon is a fraction of the size, running 277 miles long, up to 18 miles wide, and with a depth of only up to a little over a mile.[…]

Source: NASA’s Photo Shows Mars’ Grand Canyon in Spectacular Detail