Anisotropic optical scattering within Saturn's rings

Visual photometric-function data for Saturn's rings are analyzed in terms of elementary anisotropic-scattering radiative-transfer models which involve the Henyey-Greenstein function. Limits are placed on the combinations of single-scattering albedo and backscattering directivity which are permitted by observation. Particles with both microscopic and macroscopic lunarlike scattering properties are excluded by the analysis. Results are consistent with the ring particles being nearly pure spherical conglomerates of H2O frost.