NASA's Astronomy Picture of the Day for October 9, 2026 featured Stickney Crater, the largest crater on the Martian moon Phobos. The crater is named for Chloe Angeline Stickney Hall, a mathematician and wife of astronomer Asaph Hall, who discovered both moons of Mars in 1877. Stickney measures over 9 kilometers across, nearly half the diameter of Phobos, suggesting the impact that formed it may have come close to shattering the small moon.

The enhanced-color image was recorded by the HiRISE camera aboard the Mars Reconnaissance Orbiter during a pass within some six thousand kilometers of Phobos in March 2008. Although Phobos has less than 1/1000th of Earth's surface gravity, streaks in the image suggest loose material slid down the crater walls over time, and light bluish areas near the rim may indicate a relatively freshly exposed surface. The origin of the curious grooves along the moon's surface remains unexplained, though they may relate to tidal stresses or the impact itself. The image is credited to HiRISE, MRO, LPL (University of Arizona) and NASA.