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Chaotic motions of Prometheus and Pandora

Goldreich, Peter and Rappaport, Nicole (2003) Chaotic motions of Prometheus and Pandora. Icarus, 162 (2). pp. 391-399. ISSN 0019-1035.

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Recent HST images of the Saturnian satellites Prometheus and Pandora show that their longitudes deviate from predictions of ephemerides based on Voyager images. Currently Prometheus is lagging and Pandora leading these predictions by somewhat more than 20◦. We show that these discrepancies are fully accounted for by gravitational interactions between the two satellites. These peak every 24.8 d at conjunctions and excite chaotic perturbations. The Lyapunov exponent for the Prometheus-Pandora system is of order 0.35 yr^−1 for satellite masses based on a nominal density of 1.3 g cm^−3. Interactions are strongest when the orbits come closest together. This happens at intervals of 6.2 yr when their apses are anti-aligned. In this context we note the sudden changes of opposite signs in the mean motions of Prometheus and Pandora at the end of 2000 occured shortly after their apsidal lines were anti-aligned.

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Additional Information:Author preprint. We thank R. French for providing us with a copy his preprint which contains the latest results on the motions of Prometheus and Pandora, and for allowing us to reproduce from it the material in our Fig. 12. We are grateful to R. Jacobson for advice on initializing our integrations in a manner compatible with the Voyager ephemerides. Research by PG was supported by NSF grant AST-0098301 and that by NR by NASA Planetary Geology and Geophysics grant 344-30-53-02. Submitted title: Chaotic Motions of F-Ring Shepherds
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NASA Planetary Geology and Geophysics344-30-53-02
Subject Keywords:Satellites of Saturn, Orbits, Chaos
Record Number:CaltechAUTHORS:GOLicarus03a
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ID Code:2439
Deposited By: Archive Administrator
Deposited On:04 Apr 2006
Last Modified:28 Feb 2013 17:14

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