Early Mars

Early Mars

Colorado River; Nanedi Vallis

The Colorado River canyon, just above Grand Canyon (left), and Nanedi Vallis on Mars (right) pictured at the same scale shows how both canyons were formed by rivers that appear to have been approximately the same width. The river channel on Earth looks darker because it is filled with water, whereas Nanedi Vallis has been dry for billions of years.

IMAGE: Sonny Harman/Penn State