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The determination of the structure of Saturn’s F ring by nearby moonlets

Abstract

Saturn’s narrow F ring exhibits several unusual features that vary on timescales of hours to years. These include transient clumps, a central core surrounded by a multistranded structure and a regular series of longitudinal channels associated with Prometheus, one of the ring’s two ‘shepherding’ satellites. Several smaller moonlets and clumps have been detected in the ring’s immediate vicinity, and a population of embedded objects has been inferred. Here we report direct evidence of moonlets embedded in the ring’s bright core, and show that most of the F ring’s morphology results from the continual gravitational and collisional effects of small satellites, often combined with the perturbing effect of Prometheus. The F-ring region is perhaps the only location in the Solar System where large-scale collisional processes are occurring on an almost daily basis.

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Figure 1: Sequence of 360° mosaics of the F ring showing evidence for a series of collisional events between December 2006 and May 2007.
Figure 2: Comparison of a re-projected mosaic with the results of a numerical simulation of jet formation and evolution.
Figure 3: Evidence for embedded satellites on eccentric orbits near the core of the F ring.
Figure 4: Dynamical structures on a variety of scales in the F ring.

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Acknowledgements

C.D.M., K.B., N.J.C., M.W.E. and G.A.W. are grateful to the UK Science and Technology Facilities Council for financial support. The success of the FMOVIE observations described in this paper is due to the invaluable assistance of M. Showalter and the Cassini VIMS team. The authors also wish to thank R. Nelson, D. McNeil, J. Burns and our other colleagues on the Cassini project for numerous discussions.

Author Contributions C.D.M. led the research, worked on image analysis and carried out the jet simulations. K.B. and M.W.E. wrote database and image analysis software, and contributed to image sequence design. Satellite and ring orbit analysis was done by N.J.C., as were the simulations of S/2004 S 6 encountering the F ring. Simulations of planar ring–satellite interactions were done by G.A.W. C.D.M., K.B., N.J.C., M.W.E., G.A.W. and S.C. all contributed to the theories discussed.

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Correspondence to Carl D. Murray.

Supplementary information

Supplementary information

The file contains Supplementary Figures 1-10 with Legends; Supplementary Tables 1-2 with Legends and Supplementary Video Legends 1-4. (PDF 1554 kb)

Supplementary information

The file contains Supplementary Video 1 showing animation of a massive S/2004 S 6 crossing a massless F ring core. (MOV 4487 kb)

Supplementary information

The file contains Supplementary Video 2 showing animation of a massive S/2004 S 6 crossing a massless F ring core viewed from two different angles. (MOV 2951 kb)

Supplementary information

The file contains Supplementary Video 3 showing a numerical simulation of the effect of a ~5 km-radius satellite on a circular, 50 km-wide ring of test particles followed over one orbital period and viewed in a rotating reference frame. (MOV 601 kb)

Supplementary information

The file contains Supplementary Video 4 showing a numerical simulation of the effect of a conjunction between Prometheus and a ~5 km-radius satellite on a circular, 50 km-wide ring of test particles followed over one orbital period and viewed in a rotating reference frame. (MOV 2812 kb)

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Murray, C., Beurle, K., Cooper, N. et al. The determination of the structure of Saturn’s F ring by nearby moonlets. Nature 453, 739–744 (2008). https://doi.org/10.1038/nature06999

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