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Explanation: Mars has two tiny moons, Phobos and Deimos, named for the figures in Greek mythology Fear and Panic. Detailed surface views of smaller moon Deimos are shown in both these panels. The images were taken in 2009, by the HiRISE camera on board the Mars Reconnaissance Orbiter spacecraft, NASA's long-lived interplanetary internet satellite. The outermost of the two Martian moons, Deimos is one of the smallest known moons in the Solar System, measuring only about 15 kilometers across. Both Martian moons were discovered in 1877 by Asaph Hall, an American astronomer working at the US Naval Observatory in Washington...

Explanation: Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even...

HiRISE image of Stickney Crater on Phobos. Credit: NASA/JPL/University of Arizona. Stickney crater is almost half the diameter of Phobos itself. Why did the impact not shatter this small moon? The color picture above is a composite from two pictures taken about 10 minutes apart in order to give the 3-dimensional aspect. A recent Picture of the Day described some of the large-scale formations on Phobos, especially Stickney Crater, but this more dramatic picture, which has recently become available, deserves another showing because it portrays the distinctive features of an Electric Discharge Machining (EDM) event with greater clarity. The...