Are Saturn’s rings actually young?

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Abstract

Spectacular results from Cassini’s Grand Finale have provided constraints on the characteristics and evolutionary processes of Saturn’s rings. These results have been interpreted as proof that the rings are much younger than the Solar System, dramatically changing our view of the origin of the whole Saturnian system and attracting the attention of scientific media outlets. But we should keep in mind that the age of the rings has not actually been measured (which is impossible per se) but rather is inferred. Here, we put these latest results into perspective and we point out that the young-rings hypothesis has some unsolved problems. Other interpretations, compatible with rings as old as the Solar System, are still possible.

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Fig. 1: Time evolution of the mass of the rings from numerical simulations of their viscous spreading between 60,000 km (Saturn’s surface) and 140,000 km (the Roche radius).

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Acknowledgements

A.C. thanks C. Dalle-Ore, E. Rivera-Valentin and M. Kirchoff for enlightening discussions. S.C. acknowledges support from the CNES (French space agency) as well as financial support from the UnivEarthS Labex programme of Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02). H.-W.H. acknowledges support from the Cassini project and NASA ROSES NNH15ZDA001N-CDAPS. L.D. acknowledges support from the Cassini project.

Author information

A.C. initiated and coordinated this work. S.C. ran the simulations and produced the figure. All of the authors contributed to the planning and writing of the manuscript.

Correspondence to Aurélien Crida.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Joshua Colwell and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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