... Deimos: A Small Martian Moon . ... Mars has two tiny moons, Phobos and Deimos. Pictured above is Deimos, the smaller moon of Mars. In fact, Deimos is one of the smallest known moons in the Solar System measuring only nine miles across. Comet Wild 2s Nucleus from Stardust . ... What does a comet nucleus look like? ... The icy centers of comets are usually hidden from Earth-bound telescopes by opaque dust and gas that boils off during approach to the Sun. ... A Dust Devil Crater on Mars . ...