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Saturn has 61 moons with confirmed orbits, 52 of which have names, and most of which are quite small. There are also hundreds of known "moonlets" embedded within Saturn's rings. With seven moons that are large enough to be rounded in shape (and which would thus be considered dwarf planets if they were in direct orbit about the Sun) in addition to the planet's broad and dense rings, the Saturnian system is the most diverse in the solar system. Particularly notable are Titan, with an earth-like atmosphere and a landscape including hydrocarbon lakes and river networks, and Enceladus, which may harbor liquid water under its south pole. Twenty-three of Saturn's moons are regular satellites, with prograde orbits that are not greatly inclined with respect to Saturn's equatorial plane. In addition to the seven major satellites, an additional four moons are small trojans that share an orbit with a larger moon, and two more are mutually co-orbital moons. Finally, two moons are known to orbit within gaps in Saturn's rings. The regular satellites are traditionally named after Titans or other figures associated with the mythological Saturn. The remaining thirty-eight, all small, are irregular satellites, whose orbits are much farther from Saturn, have high inclinations, and are mixed between prograde and retrograde. These moons were likely captured minor planets, or debris from the breakup of such bodies after they were captured, creating collisional families. The irregular satellites have been classified by their orbital characteristics into Inuit, Norse, and Gallic groups, and their names are chosen from the corresponding mythologies. The Moons of Saturn are broken into several groups: Inner large moons The innermost large moons of Saturn orbit within its tenuous E Ring. They are: Mimas, the "Death Star" moon, with a deep crater one fifth its diameter; Enceladus, a bright, striped moon whose geysers are the source of the E Ring; Tethys, with a canyon running three-quarters its circumference that formed when an internal ocean froze; Dione, with wispy terrain on its trailing hemisphere. Hyperion Outer large moons Saturn's largest moons all orbit beyond its E Ring and can thus be considered a distinct group. They are: Rhea, which may have its own ring system; Titan, a huge moon, with methane lakes, sand dunes made of organic material, and an atmosphere thicker than Earth's; Hyperion, a smallish, tumbling moon that looks like a sponge; (See Photo ) Iapetus, a two-toned, walnut-shaped moon with an equatorial ridge. Co-orbitals Janus and Epimetheus are co-orbital moons. These two moons are of roughly equal size and have orbits with only a few kilometers difference in diameter, close enough that they would collide if they attempted to pass each other. Instead of colliding, however, their gravitational interaction causes them to swap orbits every four years. Name: Class: Date: Trojan moons Trojan moons orbit at the same distance from Saturn but never meet. Trojan moons are another kind of co-orbital. Like the other co-orbitals, they are a feature unique to the Saturnian system. They are moons that orbit at exactly the same distance from Saturn as another moon, but at such a distance from the other moon that they never collide. Tethys has two tiny co-orbitals Telesto and Calypso, and Dione also has two, Helene and Polydeuces. Ring shepherds Shepherd satellites are moons that orbit within, or just beyond, a planet's ring system. Their role is to use their gravitation pull to keep the ring particles in line and maintain the gaps in between each ring. They have the effect of sculpting the rings: giving them sharp edges, and creating gaps between them. Saturn's shepherd moons are the moonlets, Pan, Daphnis, Atlas, Prometheus, Pandora, S/2008 S 1, in addition to the unconfirmed moons S/2004 S 4, S/2004 S 6 and S/2004 S 3. Irregular moons Irregular satellites of Saturn. Irregular moons are small satellites with large-radius, inclined, and sometimes retrograde orbits, believed to have been acquired by the parent planet through a capture process. They often occur as collisional families. The largest Saturnian irregular by far, and the only one known in any detail, is Phoebe. Moonlets: In 2006, four tiny "moonlets" were found in Cassini images of the A Ring. These objects are large enough to clear partial gaps in the rings. The moonlets themselves are tiny, ranging from about 40ā500 meters in diameter, and are too small to be seen directly. In 2007, the discovery of 150 more moonlets revealed that they are confined to three narrow bands in the A Ring about 130,000 km from Saturn's center it is likely they were formed from the breakup of larger bodies. It is estimated that the A Ring contains thousands of such fragments. Questions: 1) What is the role of a Shepherd moon? Mimas or the Death Star? 2) Why are scientists excited about Titan? 3) What is unusual about Trojan moons? 4) What is the most probable reason for the large amount of moons orbiting Saturn? 5) Which moon provides the material making up the āeā ring?