Blog Post Image: Study: Greenhouse gas might have warmed early Mars enough to allow liquid water

A river ran through it: A split panel comparing a section of Arizona’s Grand Canyon, left, with a section of Mars’ Nanedi Valles in the Lunae Palus quadrangle of Mars. The northern part of the image shows that a river once cut through it similar to the one flowing through the Grand Canyon. Image credit: NASA / JPL (Click image to enlarge)