During the first billion years of existence, Mars was an active and violent place with volcanic eruptions, meteor showers, and huge floods cutting channels across its surface. Since then, lava and wind have continued to mold its shape into strange and beautiful formations, like this dune field in Herschel Basin which appears to be cemented in place.

(Text adapted from and photograph shot on assignment for "A Mars Never Dreamed Of," February 2001, National Geographic magazine)