Structure, stability and evolution of Saturn's rings

Recent data obtained from the Voyager spacecrafts and ground-based measurements indicate: (1) the rings have a thickness of at most 150 m (ref. 1) and probably several times less 2,3 ; (2) the rings are mostly composed of ice particles ranging from centimetres to metres in size 4 ; (3) the rings are subdivided into a large number of ringlets with a radial dimension ranging from 10-km down to the several metres resolution of the Voyager spacecraft's camera 5 ; (4) the B ring contains very many optical depth variations (0.6–3) 3 . This behaviour is essentially determined by the collisional properties of the rings' ice particles. Here we report some preliminary results from an experiment designed to measure the coefficient of restitution of ice particles colliding at impact velocities relevant to Saturn's rings. We apply these results to simple dynamical models for Saturn's rings and deduce the rings' thickness to be ≺5 m. We also show that regions with optical depth