The dominant feature on the surface of Mars’ largest satellite, Phobos, is Stickney — a 9-kilometre-wide mega crater that spans nearly half the moon. The crater lends Phobos a physical resemblance to the planet-destroying Death Star in the film “Star Wars.” But over the decades, understanding the formation of such a massive crater has proven elusive for researchers.
Orbiting a mere 3,700 miles above the surface of Mars, Phobos is closer to its planet than any other moon in the solar system. Mars’ gravity is drawing in the 17 × 14 × 11 mile body by about 6.6 feet (2 metres) every hundred years. The long, shallow grooves lining the surface of Phobos are likely early signs of its structural failure as scientists expect it to be pulled apart.