Comparative planetary science closest analogue is the Pluto-Charon system, though its axial tilt is completely different. Both our Moon and Charon are hypothesized to have formed via giant impacts. Giant impacts are hypothesized to account for both the tilt of Uranus, and the retrograde rotation of Venus. Giant impacts are also candidates for the Mars ocean hypothesis, and the high density of Mercury. Most giant planets (except Neptune) have retinues of moons, rings, ring shepherds, and moon Trojans analogous to mini-solar systems. These systems are postulated to have accreted from analogous gas clouds, and possibly with analogous migrations during their formation periods. The
Exploration of Uranus cloud tops. This was the probe's first solo planetary flyby, since "Voyager 1" ended its tour of the outer planets at Saturn's moon Titan. Uranus is the third-largest planet in the Solar System. It orbits the Sun at a distance of about and completes one orbit every 84 years. The length of a day on Uranus as measured by "Voyager 2" is 17 hours and 14 minutes. Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the Solar