Stickney Crater . ... Credit Copyright: HiRISE , MRO , LPL (U. Arizona) , NASA 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. ... Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth's gravity, streaks suggest loose material slid down inside the crater walls over time. ...