Jupiter's ring system: New results on structure and particle properties

Abstract

A reexamination of the Voyager images has yielded a refined understanding of Jupiter's diffuse ring system. The system is composed of a relatively bright narrow ring and inner toroidal halo, in addition to the exterior “gossamer” ring discussed elsewhere (Showalter et al., 1985, Nature 316, 526–528). The previously suspected inner disk is absent. The main ring is ∼7000 km wide and has an abrupt outer boundary at a radius of 129,130 ± 100 km. Visible in the ring are several narrow bright features, which may bear some relationship to Adrastea and Metis; these features appear to be narrower and relatively brighter in backscatter. The smallest ring particles obey a power law size distribution, and have an optical depth of 1–6 × 10 −6 for grains up to 100 μm in radius. The largest bodies are dark, rough, and red, and of comparable total optical depth. The halo arises at the bright ring's inner boundary and rapidly expands inward to a ∼20,000-km full thickness, but remains symmetric about the ring plane. It disappears from sight at a radius of 90,000 km, roughly halfway between the main ring and the planet's cloudtops. The halo particles are not predominantly Rayleigh scatterers; they appear to obey a size distribution similar to that of the micron-sized population in the main ring, and comprise a similar optical depth.