JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

We propose to analyze spectral and phase photometry of Jupiter's three rings to constrain the size distribution, composition, and spatial distribution of particles in the ring system. We will then apply a physical model of ring evolution to the main ring. Our evolutionary model will constrain the physical processes in the ring, the characteristics of ring particles which are not directly observable, and the origin and evolution of the ring. This global, long-term model complements and builds on existing models for the short-term dynamics of ring particles. Using a combination of two models developed at the University of Colorado, we have successfully modeled the optical properties and evolution of similar dusty rings. Our optical model, C-PHOT, treats the light scattering properties of realistic, rough-surfaced, non-spherical particles with scattering inclusions. This model constrains the composition and size distribution of visible particles based on spectra and phase curves of the ring. Our evolutional model, C-EVOL, tracks the size distribution of a dusty ring from its initial creation by the breakup of a progenitor satellite, until a steady-state ring is achieved. All relevant physical processes are included. These models have been extensively used on ring systems similar to Jupiter's, including the ringbelts of Uranus and Neptune and the faint G ring of Saturn (Colwell and Esposito 1990a, 1990b, 1992, 1993; Canup and Esposito 1997; Throop and Esposito 1998). Galileo's ring observations include visible images and UV and IR spectra, all from a range of phase angles. Our analysis to date of Galileo data indicates that the rings' IR spectrum is consistent with that from a shallow power-law size distribution of silicate scatterers, and does not requite a significant optical depth of larger bodies (e.g., Showalter et al. 1987). Our size distribution is consistent with that evolved from a young, disrupted satellite. As an E/PO activity, we will work with local high school physics and math teachers to develop a set of curriculum materials. The curriculum will emphasize enabling students to use their abilities in math and physics to address fundamental issues of astronomy and methods of doing science. These materials will be distributed through teacher workshops and regional science teacher conferences.