Washington, April 10 : The High Resolution Imaging Science Experiment (HiRISE) has produced a new color stereo view of Phobos, the larger and inner of Mars' two tiny moons.
Run from the University of Arizona (UA), the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter took two images of Phobos 10 on March 23. Scientists combined the images for a stereo view.
Earlier, Mars Global Surveyor has taken higher resolution pictures of Phobos.
"But the HiRISE images are higher quality, making the new data some of the best ever for Phobos," said HiRISE team member Nathan Bridges of NASA's Jet Propulsion Laboratory, in Pasadena, California. "The new images will help constrain the origin and evolution of this moon," he added.
"Phobos is of great interest because it may be rich in water ice and carbon-rich materials," said professor Alfred McEwen of the UA's Lunar and Planetary Laboratory, and HiRISE principal investigator.
By combining information from the HiRISE camera's blue-green, red and near-infrared color channels, scientists confirmed that material around the rim of Phobos' largest surface feature, Stickney crater, appears bluer than the rest of Phobos.
"If Phobos' surface is analogous with surface of our own moon, the bluer color could mean that the regolith is fresher, or hasn't been exposed to space as long as the rest of Phobos' surface has," said Bridges.
The HiRISE view also shows landslides along the walls of Stickney and other large craters, Phobos' striking surface grooves and crater chains, and craters hidden on the moon's dark side illuminated by "Marsshine."
"Marsshine" is sunlight reflected by Mars onto the moon. The phenomenon is analogous to "Earthshine," where Earth reflects sunlight that illuminates the dark side of our moon.
Phobos was 6,800 kilometers, or about 4,200 miles, away when the HiRISE camera took the first photograph. At that distance, the HiRISE camera was able to resolve surface features at a scale of 6.8 meters, or about 22 feet, per pixel, and see features as small as 20 meters, or 65 feet, across.
Phobos was 5,800 kilometers, or about 3,600 miles, away when the HiRISE camera took the second picture minutes later. At that distance, the HiRISE camera was able to resolve features about 15 meters, or 50 feet, across.
By combining HiRISE and CRISM data on Phobos, scientists can map minerals and soil types on the moons.