Mars' largest moon, Phobos, has captured public imagination because the dominant feature on its surface (22-kilometers across) is Stickney crater (9-km across), a 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. For the first time, physicists at Lawrence Livermore National Lab have demonstrated how an asteroid or comet impact could have created Stickney crater without destroying Phobos completely. The research, which also debunks a theory regarding the moon's mysterious grooved terrain, was published in Geophysical Review Letters.