New views of Mars from THEMIS, an infrared camera aboard NASA's Mars Odyssey spacecraft, are allowing earthbound scientists to decode the storied geological history of our neighboring planet. Slight variations in composition or texture, which can record the action of wind or water, pop out in an infrared view because they affect the way the surface radiates heat. Philip Christensen, a planetary scientist at Arizona State University, used this new capability to study the unusual landscape of Terra Meridiani (above), a region of outcrops on Mars analogous to the buttes and bluffs of northern Arizona. The infrared views show that distinct layers of rock, once continuous, have eroded in a complex pattern. Christensen suspects the layers were created by the movement of subsurface water, but other researchers have considered volcanic deposits or strong winds in an earlier, thicker atmosphere. New color snapshots from Themis will help clear up the debate. Each spectral band in the camera's rainbow images signifies a different mineral. Carbonate rocks, which form only in the presence of liquid water, would prove that oceans and lakes once reshaped the dusty surface of Mars.
Photograph courtesy of NASA/JPL