Saturn's rings

and A. The 'Cassini Division' is the largest gap in the rings and separates Rings B and A (named after Jean-Domenique Cassini who discovered the gap in 1676). In addition a number of fainter rings have been discovered more recently. The D Ring is exceedingly faint and closest to the planet. The F Ring is a narrow feature just outside the A Ring. Beyond that are two far fainter rings named G and E. The particles in Saturn's rings are composed primarily of water ice and range from microns to metres in size. The rings show a tremendous amount of structure on all scales; features like spokes and irregular ripples， known as C， as yet undiscovered， Galileo Galilei， very close to Saturn's rings. Some of this structure is related to gravitational perturbations by Saturn's many moons， working outward from the planet， are puzzling. Some of them might be signs of asteroids plunging through the ring system， B， or others might be caused by tiny moonlets， but much of it remains unexplained. The Cassini-Huygens mission explored the rings intensively to throw light on these mysteries. ， 1564-1642 The puzzles have only increased since NASA's Voyager 1 and 2 missions imaged the ring system extensively in 1980 and 1981. The rings have been given letter names in the order of their discovery. The main rings are，。