Phobos (moon) break up when it reaches approximately 2.1 Mars radii. When Phobos is eventually torn apart by tidal forces, a fraction of the debris will likely form a planetary ring around Mars, which may last from one million to one hundred million years. The origin of the Martian moons is still controversial. Phobos and Deimos both have much in common with carbonaceous C-type asteroids, with spectra, albedo, and density very similar to those of C- or D-type asteroids. Based on their similarity, one hypothesis is that both moons may be captured main-belt asteroids. Both moons have very circular orbits which lie
Wonders of the Solar System he examines how the Cassini–Huygens space-probe's imagery provides an insight on the highly complex structure of the ice rings of Saturn, and its diverse array of moons, and how they can reveal insights into the formation and evolution of the solar system. He also explains how Enceladus, as the most reflective object in the known universe, has been of interest due to its continental divide-like canyons and geysers (as also observed in parts of Iceland). In the Sahara Desert the formative effect of winds on sand-dune morphology is paralleled to that of the gravitational effect of Saturn's 61 known moons