Science Source Feb 2010

This image from NASA's Mars Odyssey spacecraft shows the checkerboard region of Noctis Labyrinthus, the Labyrinth of Night, west of the immense equatorial gash of Valles Marineris. This feature's origins are not certain, but scientists think it began to develop when volcanic activity stirred in the adjoining region of Tharsis, stretching the Martian crust and fracturing it. As cracks and faults opened, ice and water in the subsurface escaped, making the ground collapse. The result today is a tangle of tablelands cut by canyons, troughs, and pits. This false-color Thermal Emission Imaging System (THEMIS) mosaic focuses on one junction where canyons meet to form a depression 4 kilometers (13,000 feet) deep. The mosaic combines visible wavelength images made during daytime with nighttime infrared images. The nighttime view records the predawn temperature of the surface. This data can tell scientists about the nature of the materials on the ground. As on Earth, debris that tumbles down canyon walls ranges in size from large boulders down to fine-grain material such as gravel, sand, and dust. Here, dark streaks mark the paths of sand or dust avalanches. At the foot of the slope, lie the traces of older, more substantial avalanches that piled up rocks and large debris. The heat-seeking eye of THEMIS can spot the coarser and rockier portions of a landslide's debris by their residual warmth, shown in redder tints in the image. Late at night, rocky debris on Mars is still radiating heat absorbed during daytime, just as asphalt pavement does on Earth. At the same time of night, however, patches of ground mantled in dust (shown in bluer tints) have long since cooled off.