An Aggregate Model for the Particle Size Distribution in Saturn’s Rings

Saturn’s rings are known to consist of a large number of water ice particles. They form a flat disk, as the result of an interplay of angular momentum conservation and the steady loss of energy in dissipative particle collisions. For particles in the size range from a few centimeters to about a few meters a power law distribution of radii ∼ r−q, with q ≈ 3, is implied by the light scattering properties of the rings [1, 2, 3, 4]. In contrast, for larger sizes the distribution drops steeply [5, 6, 7, 8] with increasing r. It has been suggested that this size distribution may arise from a balance between aggre