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Science 7 December 2007:
Vol. 318. no. 5856, pp. 1602 - 1607
DOI: 10.1126/science.1143977
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Research Articles

Saturn's Small Inner Satellites: Clues to Their Origins

C. C. Porco,1* P. C. Thomas,2 J. W. Weiss,1 D. C. Richardson3

Cassini images of Saturn's small inner satellites (radii of less than ~100 kilometers) have yielded their sizes, shapes, and in some cases, topographies and mean densities. This information and numerical N-body simulations of accretionary growth have provided clues to their internal structures and origins. The innermost ring-region satellites have likely grown to the maximum sizes possible by accreting material around a dense core about one-third to one-half the present size of the moon. The other small satellites outside the ring region either may be close to monolithic collisional shards, modified to varying degrees by accretion, or may have grown by accretion without the aid of a core. We derived viscosity values of 87 and 20 square centimeters per second, respectively, for the ring material surrounding ring-embedded Pan and Daphnis. These moons almost certainly opened their respective gaps and then grew to their present size early on, when the local ring environment was thicker than it is today.

1 Cassini Imaging Central Laboratory for Operations (CICLOPS), Space Science Institute, 4750 Walnut Street, Boulder, CO 80301, USA.
2 Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA.
3 Department of Astronomy, University of Maryland, College Park, MD 20742, USA.

* To whom correspondence should be addressed. E-mail: carolyn{at}ciclops.org

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Equatorial Ridges of Pan and Atlas: Terminal Accretionary Ornaments?.
S. Charnoz, A. Brahic, P. C. Thomas, and C. C. Porco (2007)
Science 318, 1622-1624
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Science. ISSN 0036-8075 (print), 1095-9203 (online)