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Origin of Saturn’s rings and inner moons by mass removal from a lost Titan-sized satellite

Nature volume 468, pages 943946 (16 December 2010) | Download Citation

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Abstract

The origin of Saturn’s rings has not been adequately explained. The current rings are more than 90 to 95 per cent water ice1, which implies that initially they were almost pure ice because they are continually polluted by rocky meteoroids2. In contrast, a half-rock, half-ice mixture (similar to the composition of many of the satellites in the outer Solar System) would generally be expected. Previous ring origin theories invoke the collisional disruption of a small moon3,4, or the tidal disruption of a comet during a close passage by Saturn5. These models are improbable and/or struggle to account for basic properties of the rings, including their icy composition. Saturn has only one large satellite, Titan, whereas Jupiter has four large satellites; additional large satellites probably existed originally but were lost as they spiralled into Saturn6. Here I report numerical simulations of the tidal removal of mass from a differentiated, Titan-sized satellite as it migrates inward towards Saturn. Planetary tidal forces preferentially strip material from the satellite’s outer icy layers, while its rocky core remains intact and is lost to collision with the planet. The result is a pure ice ring much more massive than Saturn’s current rings. As the ring evolves, its mass decreases and icy moons are spawned from its outer edge7 with estimated masses consistent with Saturn’s ice-rich moons interior to and including Tethys.

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Change history

  • 18 November 2014

    In the citation, the page range has been corrected (it was ‘943-926’).

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Acknowledgements

I thank W. R. Ward and L. Dones for detailed comments. Support from NASA’s Outer Planets Research Program is gratefully acknowledged.

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  1. Planetary Science Directorate, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado 80302, USA

    • Robin M. Canup

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Competing interests

The author declares no competing financial interests.

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Correspondence to Robin M. Canup.

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    Supplementary Information

    This file contains Supplementary Information and Data 1-9, Supplementary Figures 1-3 with legends and additional references.

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https://doi.org/10.1038/nature09661

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