The eccentric Saturnian ringlets at 1.29 Rs and 1.45 Rs

Abstract

The shapes and kinematics of the two major eccentric ringlets in Saturn's C ring are studied in data acquired by four Voyager experiments: imaging science (ISS), radio science (RSS), ultraviolet spectrometer (UVS), and photopolarimeter (PPS). It is found that the ringlets have mean widths of ∼25 km (Titan, 1.29 R s) and ∼64 km (Maxwell, 1.45 R s), eccentricities of order 10 −4, sharp edges on a scale of ∼1 km, normal optical depths τ ∼ 1−2, and are embedded in essentially empty gaps ( τ < 0.05). In addition, they exhibit positive linear width-radius relations, suggesting that differential precession across the ringlets is being prevented by the self-gravity of the ring particles. The kinematics of the Maxwell ringlet are determined solely by Saturn's nonspherical gravity field; the kinematics of the Titan ringlet are apparently determined by its interaction with Titan. Masses, mean surface mass densities, and mass extinction coefficients have been calculated. The comparatively large optical depths and mass extinction coefficients in these features suggest an environment and particle size distribution different from the remainder of the C ring and presumably caused by the mechanism responsible for ring confinement.