Stickney Crater

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 last month. Even though the surface gravity of asteroid-like Phobos
is less than 1/1000th Earth's gravity, streaks suggest loose material has
slid down inside the crater walls over time. Light bluish regions near the
crater's rim could indicate a relatively freshly exposed surface. The origin
of the curious grooves along the surface is mysterious but may be related to
the crater-forming impact.