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Published September 1989 | public
Journal Article

Saturn's main ring particle size distribution: An analytic approach

Abstract

An analytic theory for Saturn's ring particle size distribution is developed using the so-called "dynamic ephemeral bodies" (or DEBs) model of ring particles (S.J. Weidenschilling, C.R. Chapman, D.R. Davis, and R. Greenberg, 1984, in Planetary Rings, pp. 367–416, Univ. of Arizona Press, Tucson). Accretion and erosion criteria are defined, and the fundamental integrodifferential equation describing the collisional evolution of the mass distribution function of ring particles is derived in the approximation that the ring velocity dispersion is independent of the particle size. A simple stationary solution of this equation is developed, which reproduces all the main features of the distributions determined from the Voyager I radio data (H.A. Zebker, E.A. Marouf, and G.L. Tyler, 1985, Icarus 64, 531–568). The main results of this work are the following: (i) the upper cutoff of the distribution can be explained by a relative enhancement of the erosion of the large particles; (ii) the power-law index of the distribution can be related to parameters characterizing the particle collisional properties; (iii) the model yields estimates for the particle life times and for the dispersion velocity in various unperturbed regions of the rings; (iv) "hard-sphere" ring particle models are most probably ruled out, because they lead to stationary distribution functions in disagreement with the Voyager results.

Additional Information

© 1989 Published by Elsevier. Received 25 October 1988, Revised 13 February 1989. 1 thank Peter Goldreich for a number of fruitful discussions, as well as for a careful reading of a preliminary version of the manuscript and the numerous improvements he suggested. I thank D. Davis for a number of relevant physical comments, and an anonymous referee whose very thorough report on the manuscript is sincerely appreciated. Parts of this research were supported by the NSF under Grant AST 86-12799.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023