Deimos, the smaller and outermost of Mars’ two moons, is roughly oval in shape and has a deep depression at its south pole. Unlike its heavily scarred sister moon, Phobos, Deimos is covered by a loose layer of dust and rubble—a so-called regolith layer—which gives it a smoother, dustier appearance. Although numerous space probes have provided increasingly detailed images of its surface over the past decades, the origins of the debris layer and the depression at the south pole remain unclear.