Phobos, the larger of Mars' two moons, via NASA's Mars Reconnaissance Orbiter

This stereoscopic picture of Phobos, the larger of Mars' two moons, was taken on March 23 by a high-resolution camera on NASA's Mars Reconnaissance Orbiter. | Handout/University of Arizona Lunar and Planetary Laboratory / MCT

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Robert S. Boyd | McClatchy Newspapers

This stereoscopic picture of Phobos, the larger of Mars' two moons, was taken on March 23 by a high resolution camera on NASA's Mars Reconnaissance Orbiter.

The camera shot two pictures, 10 minutes apart, which show the moon's features in unprecedented detail. Phobos is only 13-1/2 miles in diameter and weighs less than 1,000th as much as Earth. Its gravity is too weak to pull it into a spherical shape. The main crater, 5-1/2 miles across, was excavated by an object that almost shattered the moon. Landslides along the walls of the crater are visible.

The camera, known as HiRISE (CQ) is operated by the University of Arizona's Lunar and Planetary Laboratory in Tucson. It can distinguish features as small as 50 feet across from an altitude of 3,600 miles.

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