37th DPS Meeting, 4-9 September 2005
Session 62 Planetary Rings I
Oral, Friday, September 9, 2005, 9:00-10:30am, Music Concert Hall

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[62.02] Structure of Saturn's Rings from Cassini Diametric Radio Occultations

E. Marouf (San Jose State U.), R. French (Wellesley Coll.), N. Rappaport, A. Kliore (JPL), M. Flasar (NASA-GSFC), A. Nagy (U. Michigan), C. McGhee (Wellesley Coll.), P. Schinder (NASA-GSFC), A. Anabtawi, S. Asmar, E. Barbinis, D. Fleischman, G. Goltz, D. Johnston, D. Rochblatt (JPL), F. Thomson (Stanford U.), K. Wong (San Jose State U.)

Cassini orbits around Saturn were designed to provide eight optimized radio occultation observations of Saturn's rings during summer, 2005. Three monochromatic radio signals (0.94, 3.6, and 13 cm-wavelength) were transmitted by Cassini through the rings and observed at multiple stations of the NASA Deep Space Network. A rich data set has been collected. Detailed structure of Ring B is revealed for the first time, including multi-feature dense ''core'' ~ 6,000 km wide of normal optical depth > 4.3, a ~ 5,500 km region of oscillations in optical depth (~ 1.7 to ~ 3.4) over characteristic radial scales of few hundred kilometers interior to the core, and a ~ 5,000 km region exterior to the core of similar nature but smaller optical depth fluctuation (~ 2.2 to ~ 3.3). The innermost ~ 7,000 km region is the thinnest (mean optical depth ~ 1.2), and includes two unusually uniform regions and a prominent density wave. With few exceptions, the structure is nearly identical for the three radio signals (when detectable), indicating that Ring B is relatively devoid of centimeters and smaller size particles. The structure is largely circularly symmetric, except for radius > ~ 116,600 km. In Ring A, numerous (> 40) density waves are clearly observed at multiple longitudes, different average background optical depth is observed among different occultations suggesting that the azimuthal asymmetry extends over most Ring A, and strong dependence of the observed structure on wavelength implies increase in the abundance of centimeter and smaller size particles with increasing radius. Multiple longitude observations of Ring C and the Cassini Division structure reveal remarkable variability of gaps and their embedded narrow eccentric ringlets, and a wake/wave like feature interior to the gap at ~ 118,200 km (embedded moonlet?). Wavelength dependent structure of Ring C implies abundance of centimeter size particles everywhere and sorting by size within dense embedded features.

The author(s) of this abstract have provided an email address for comments about the abstract: emarouf@email.sjsu.edu

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