From Earth based observations it was obvious that there are some gaps in Saturn's ring system, one, the Cassini division bears the name of its discoverer, Giovanni Cassini.

    It was the Voyager spacecraft which flew by Saturn in 1980 and revealed many of the secrets of the ring system. Images showed that the ring system was actually composed of over 1000 ringlets, there were even narrow ringlets in the Cassini division. Many of the ringlets were only about 2 km in diameter.

     Voyager also discovered a narrow ring between the orbits of Prometheus and Pandora, two of Saturn's rings. The ring particles are held in place by the gravitation of the moons. Any particle that begins to stray is pushed or pulled back into the ringlet. These moons have come to be known as shepherd satellites and other moons have been found to perform the same task elsewhere.

    The gaps in the rings are caused by resonance between the particles in the rings and the moons orbiting nearby. For example, a particle orbits in one of the gaps in twice the time it takes the moon Mimas to make one orbit once. This means that on every other trip, the particle passes Mimas in the same spot. The gravitational pull of Mimas eventually causes the particle to go into an elliptical orbit. This is a very unstable orbit because now the particle crosses the paths of millions of other particles. Collisions are almost certain to occur and this changes the orbits of the particles drastically. So, particles cannot remain in orbit at resonance with moons which can occur at various distances where particles orbit two or more times for each orbit of the moon.

     Voyager also discovered what appears to be spokes in the rings. These are radially oriented features in the rings. Since the inner rings rotate faster than the outer rings, these radial features should not occur. The apparent explanation for them is that Saturn's magnetic field pulls charged particles up out of the ring plane and the dust then rotates with the magnetic field. We see the dust as shadows on the rings which appear as spokes.

     There are several theories as to the origin of Saturn's rings. One theory suggests that the ring particles are leftover debris from the formation of the planet itself. Another idea is that the rings are debris from a satellite that for whatever reason was unable to form. Probably the most likely theory is that the particles are the result of an icy satellite that was shattered by an impact with a comet. Saturn's other moons do show signs of heavy cratering and this may well be the source of the Saturn's rings of fame.