Geography of Mars

Although Mars is a small planet – its radius is just a little over half of Earth's – we now know that it boasts scenery on a scale that makes Mount Everest and the Grand Canyon seem unimpressive by comparison.

Running from the eastern flanks of the rise, roughly along the equator, is Valles Marineris.
This is a split in the Martian crust 4000 kilometres long (about a fifth of the distance around the whole of Mars), up to 600 kilometres wide and seven kilometres deep. The Grand Canyon is a mere 450 kilometres long, up to 29 kilometres wide and 1.6 kilometres deep.

The Valles Marineris hemisphere of Mars