On the Martian surface, the mountains are high and the canyons are low. Really, really low.
Not only is the martian volcano Olympus Mons the highest peak in the solar system, Melas Chasma, the canyon pictured above, is the deepest in the solar system. In this image from the European Space Agency’s Mars Express orbiter, the valley on the left (darker area) sits a whopping 5.6 miles below the plateau on the right (lighter area).
Compared to the average shape of Mars, known as the “aeroid,” the canyon floor sinks down about 3.1 miles. Planetary scientists would love to use sea level measurements to describe Martian surface features, but there’s no ocean on the red planet anymore and any signs of an ocean are long since warped by millions of years of surface deformation.
The photo above covers about 7,700 square miles, or about the size of New Jersey, which makes it only a tiny postage stamp of Mars’ deepest, longest and most prominent scar — the 2,500-mile-long Valles Marineris rift valley (below).
ESA also released the following 3-D rendering of Melas Chasma in addition to the satellite imagery, revealing the valley in all its topographical glory (via Nancy Atkinson at Universe Today).