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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Lainey, V., Charnoz, S., Reboussin, L., Noyelles, B. & Baillié, K. The Cassini Division and Mimas’ eccentricity: A common history. In 44th Meet. Am. Astron. Soc. Div. Planet. Sci. 414.08 (2012).
Baillié, K., Noyelles, B., Lainey, V., Charnoz, S. & Tobie, G. Formation of the Cassini Division – I. Shaping the rings by Mimas inward migration. Mon. Not. R. Astron. Soc. 486, 2933–2946 (2019).
Zhang, Z. et al. Exposure age of Saturn’s A and B rings, and the Cassini Division as suggested by their non-icy material content. Icarus 294, 14–42 (2017).
Ida, S. The origin of Saturn’s rings and moons. Science 364, 1028–1030 (2019).
Iess, L. et al. Measurement and implications of Saturn’s gravity field and ring mass. Science 364, eaat2965 (2019).
Daisaka, H., Tanaka, H. & Ida, S. Viscosity in a dense planetary ring with self-gravitating particles. Icarus 154, 296–312 (2001).
Charnoz, S., Salmon, J. & Crida, A. The recent formation of Saturn’s moonlets from viscous spreading of the main rings. Nature 465, 752–754 (2010).
Crida, A. & Charnoz, S. Satellite formation: Spreading of rings beyond the Roche radius. In SF2A-2013: Proc. Ann. Meet. French Soc. Astron. Astrophys. 57–60 (2013).
Charnoz, S. et al. Accretion of Saturn’s mid-sized moons during the viscous spreading of young massive rings: Solving the paradox of silicate-poor rings versus silicate-rich moons. Icarus 216, 535–550 (2011).
Crida, A. & Charnoz, S. Formation of regular satellites from ancient massive rings in the Solar System. Science 338, 1196–1199 (2012).
Nicholson, P. D. & Hedman, M. M. Self-gravity wake parameters in Saturn’s A and B rings. Icarus 206, 410–423 (2010).
Crida, A. & Charnoz, S. Complex satellite systems: A general model of formation from rings. Proc. Int. Astron. Union 9, 182–189 (2014).
Salmon, J., Charnoz, S., Crida, A. & Brahic, A. Long-term and large-scale viscous evolution of dense planetary rings. Icarus 209, 771–785 (2010).
Canup, R. M. Origin of Saturn’s rings and inner moons by mass removal from a lost Titan-sized satellite. Nature 468, 943–946 (2010).
Kempf, S., Altobelli, N., Srama, R., Cuzzi, J. & Estrada, P. The age of Saturn’s rings constrained by the meteoroid flux into the system. In Am. Geophys. Union Fall Meet. 2017 abstr. P34A-05 (2017).
Cuzzi, J. N. & Estrada, P. R. Compositional evolution of Saturn’s rings due to meteoroid bombardment. Icarus 132, 1–35 (1998).
Zhang, Z. et al. Cassini microwave observations provide clues to the origin of Saturn’s C ring. Icarus 281, 297–321 (2017).
Tsiganis, K., Gomes, R., Morbidelli, A. & Levison, H. F. Origin of the orbital architecture of the giant planets of the Solar System. Nature 435, 459–461 (2005).
Morbidelli, A., Levison, H. F., Tsiganis, K. & Gomes, R. Chaotic capture of Jupiter’s Trojan asteroids in the early Solar System. Nature 435, 462–465 (2005).
Gomes, R., Levison, H. F., Tsiganis, K. & Morbidelli, A. Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Nature 435, 466–469 (2005).
Nesvorný, D., Vokrouhlický, D., Bottke, W. F. & Levison, H. F. Evidence for very early migration of the Solar System planets from the Patroclus-Menoetius binary Jupiter Trojan. Nat. Astron. 2, 878–882 (2018).
Clement, M. S., Kaib, N. A., Raymond, S. N., Chambers, J. E. & Walsh, K. J. The early instability scenario: Terrestrial planet formation during the giant planet instability, and the effect of collisional fragmentation. Icarus 321, 778–790 (2019).
Ćuk, M., Dones, L. & Nesvorný, D. Dynamical evidence for a late formation of Saturn’s moons. Astrophys. J. 820, 97 (2016).
Hyodo, R. & Charnoz, C. Dynamical evolution of the debris disk after a satellite catastrophic disruption around Saturn. Astron. J. 154, 34 (2017).
Neveu, M. & Rhoden, A. R. Evolution of Saturn’s mid-sized moons. Nat. Astron. 3, 543–552 (2019).
Kirchoff, M. R. et al. In Enceladus and the Icy Moons of Saturn (eds Schenk, P. M. et al.) 267–284 (University of Arizona Press, 2018).
Dalle Ore, C. M., Cruikshank, D. P., Mastrapa, R. M. E., Lewis, E. & White, O. L. Impact craters: An ice study on Rhea. Icarus 261, 80–90 (2015).
López-Oquendo, A. J. et al. Constraints on crater formation ages on Dione from Cassini VIMS and ISS. In 50th Lunar Planet. Sci. Conf. 2435 (2019).
Fuller, J., Luan, J. & Quataert, E. Resonance locking as the source of rapid tidal migration in the Jupiter and Saturn moon systems. Mon. Not. R. Astron. Soc. 458, 3867–3879 (2016).
Charnoz, S., Morbidelli, A., Dones, L. & Salmon, J. Did Saturn’s rings form during the Late Heavy Bombardment? Icarus 199, 413–428 (2009).
Dubinski, J. A recent origin for Saturn’s rings from the collisional disruption of an icy moon. Icarus 321, 291–306 (2019).
Lainey, V. et al. New constraints on Saturn’s interior from Cassini astrometric data. Icarus 281, 286–296 (2017).
Pan, M. & Schlichting, H. E. Self-consistent size and velocity distributions of collisional cascades. Astrophys. J. 747, 113 (2012).
Levison, H. F., Morbidelli, A., Vokrouhlický, D. & Bottke, W. F. On a scattered-disk origin for the 2003 EL61 collisional family — An example of the importance of collisions on the dynamics of small bodies. Astron. J. 136, 1079–1088 (2008).
Poppe, A. R. An improved model for interplanetary dust fluxes in the outer Solar System. Icarus 264, 369–386 (2016).
Altobelli, N., Kempf, S. & Srama, R. Dust in the Outer Solar System as measured by Cassini-CDA: KBOs, Centaurs and TNOs as parent bodies? In 2017 Eur. Planet. Sci. Congr. 11, EPSC2017–794 (2017).
Hsu, H.-W. et al. In situ collection of dust grains falling from Saturn’s rings into its atmosphere. Science 362, eaat3185 (2018).
Waite, J. R. Jr. et al. Chemical interactions between Saturn’s atmosphere and its rings. Science 362, eaat2382 (2018).
Buratti, B. J. et al. Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus. Science 364, eaat2349 (2019).
Amos, J. Cassini hints at young age for Saturn’s rings. BBC News (30 August 2017); https://go.nature.com/2SZPk5A
Drake, N. Ringless Saturn? The planet’s famous feature may be surprisingly young. National Geographic (9 April 2019); https://go.nature.com/2Ztd4Bq
Choi, C. Q. Saturn’s rings may be younger than the dinosaurs. Space (17 January 2019); https://go.nature.com/2ytZPEZ
O’Donoghue, J. et al. Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere. Icarus 322, 251–260 (2019).
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.
The authors declare no competing interests.
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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Crida, A., Charnoz, S., Hsu, HW. et al. Are Saturn’s rings actually young?. Nat Astron 3, 967–970 (2019). https://doi.org/10.1038/s41550-019-0876-y
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