Formation and evolution of the Solar System System bodies have been created by both collisions and capture. Mars's two small moons, Deimos and Phobos, are thought to be captured asteroids. The Earth's Moon is thought to have formed as a result of a single, large head-on collision. The impacting object probably had a mass comparable to that of Mars, and the impact probably occurred near the end of the period of giant impacts. The collision kicked into orbit some of the impactor's mantle, which then coalesced into the Moon. The impact was probably the last in the series of mergers that formed the Earth. It has been
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