Pastel colors swirl across Mars, revealing differences in the composition and nature of the surface in this false-color infrared image taken May 22, 2009, by the Thermal Emission Imaging System (THEMIS) camera on NASA's Mars Odyssey orbiter.
The image shows an area 19.8 miles (31.9 kilometers) by 54.9 miles (88.3 kilometers) in the southern highlands of Mars. It is a result of altering the orbit of Odyssey so that the spacecraft passes over the dayside of Mars earlier in the afternoon when the ground is warmer and emits more strongly in the infrared frequencies detected by THEMIS. Prior to beginning the slow shift in orbit September 30, 2008, Odyssey was looking down at the ground where the local solar time was about 5 p.m. When the shift was completed on June 9, 2009, the orbiter and camera were looking down at the ground where the local solar time was about 3:45 p.m.
In the image, dark areas mark exposures of relatively cold ground with abundant bare rock, while warmer basaltic sand covers the light blue-green regions. Reddish areas likely have a higher silica content, due either to a different volcanic composition or to weathering.
NASA/JPL/Arizona State University