Physical properties of Saturn's rings

A review is given of important features of the rings, touching only lightly on aspects covered by other speakers (Spokes, E ring). This extended abstract will only convey the high points of the talk.Most of the material in Saturn's rings is concentrated in the B ring, with a lesser amount in the A ring and only small amounts in the C ring and Cassini Division. There is a very different character to these classical ring regions; the C and Cassini particles are darker and more neutral in color; (Smith et al. 1981, 1982). The A and B regions contain nearly all of the “small” particles, from microns to millimeters. Overall, however, the particles are fairly well characterized by Voyager radio occultation results as roughly following an r-3powerlaw between about 1 cm and a few meters (Tyler et al. 1982, Marouf et al. 1982). A fairly sharp cutoff in the size distribution is seen at radii varying with location from about 1 to about 5 meters. The material of the ring particles is probably mostly water ice (see e.g., Pollack 1975) but the redness of the rings requires the presence of minor constitutents. Combinations of ground-based radar and radio emission observations (Pollack 1975, Cuzzi and Pollack 1978; Pettengill, this issue) strongly indicate that the non-icy component comprises a small fraction of the total bulk material. In fact, mass densities derived from density waves (e.g. Holberg et al. 1982) and CRAND measurements (Cooper et al. 1982) combined with Voyager particle size measurements indicate a particle density more like that of snow or frost than that of pure ice.