The Ocean Worlds Of Our Solar System. There are more than 100 moons in our Solar System that do their mysterious gravitational dance around the eight major planets belonging to our Sun's family. Most of them are icy and small, containing only tiny quantities of rocky material, and they circle around the quartet of giant gaseous planets that dwell in the outer regions of our Solar System. The four majestic, giant denizens of the outer limits--Jupiter, Saturn, Uranus, and Neptune--are cloaked in blankets of gas, and they are orbited by sparkling, icy moons and moonlets. Of the quartet of relatively small, rocky terrestrial planets--Mercury, Venus, Earth, and Mars--Mercury and Venus are moonless, and Mars is circled by a pathetic duo of tiny and somewhat deformed moons (Phobos and Deimos). The two little moons of Mars are interesting objects, frequently considered to be asteroids that escaped from the Main Asteroid Belt between Mars and Jupiter, only to be snared by the Red Planet's gravitational pull when our Solar System was young. Earth's own beautiful, beguiling, bewitching Moon is the only large one inhabiting the inner kingdom of our Solar System. Earlier infrared data did not have sufficient resolution to separate MK 2 from Makemake's veiling glare. The astronomers' reanalysis, however, based on the more recent HST observations, indicates that much of the warmer surface spotted earlier in infrared light may simply be the dark surface of the companion MK 2. A moon is defined as a natural satellite that orbits a larger body--such as a planet--that, in turn, orbits a star. The moon is kept in its position both by the gravity of the object that it circles, as well as by its own gravity. Some planets are orbited by moons; some are not. Some dwarf planets--such as Pluto--possess moons. In fact, one of Pluto's moons, named Charon, is almost half the size of Pluto itself, and some planetary scientists think that Charon is really a chunk of Pluto that was torn off in a disastrous collision with another object very long ago. In addition, some asteroids are also known to be orbited by very small moons.