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Hedman, M.M., Burns, J.A.,Tiscareno, M.S., Porco, C.C. (2010). "A Corrugated Curiosity in Saturn's C Ring" American Astronomical Society, DDA meeting #41, #11.02. |
Abstract
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In August of 2009 the sun passed through Saturn's equatorial plane, so Saturn's rings were illuminated from almost exactly edge-on. This unusual lighting geometry revealed a subtle corrugation extending throughout the entire C ring. Images of this structure obtained by the cameras onboard the Cassini spacecraft reveal that this corrugation has an amplitude of only a few meters and a wavelength that steadily increases with distance from the planet, ranging from 30 km near the C-ring's inner edge at 75,000 km from Saturn center to about 80 km at 92,000 km, just interior to the B-ring's inner edge. The overall radial trend in the corrugation's wavelength indicates that this structure, --like a similar corrugation previously identified in the D ring (Hedman et al. 2007 Icarus 188:89-107)-- is the result of differential nodal regression within an initially inclined ring and is sensitive to the higher-order moments of Saturn's gravity field. Small residuals from this overall trend can be ascribed to the finite surface mass density of the C ring. If our interpretation of this structure is correct, then the entire C ring was slightly tilted out of Saturn's equator plane in the early 1980s. Possible explanations for how the ring might have been disturbed at this time will be explored.
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