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Saturn's largest ring


Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter’s gossamer rings1 and Saturn’s E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128RS to 207RS (Saturn’s radius RS is 60,330 km). The ring’s vertical thickness of 40RS matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring’s normal optical depth of 2 × 10-8 is comparable to that of Jupiter’s faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward2,3 and many of them ultimately strike the dark leading face of Iapetus.

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Figure 1: Spitzer MIPS imaging in the vicinity of Saturn.
Figure 2: A subset of the Spitzer MIPS 24 μm Basic Calibrated Data images, comprising a MIPSON scan.
Figure 3: Vertical profiles through the Phoebe dust structure.
Figure 4: The orbital distribution of dust grains launched from Phoebe followed for 2,000 years.


  1. 1

    Burns, J. A. et al. The formation of Jupiter’s faint rings. Science 284, 1146–1150 (1999)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Soter, S. Remarks on origin of Iapetus’ photometric asymmetry. IAU Colloq. 28, abstract (1974)

  3. 3

    Burns, J. A., Hamilton, D. P., Mignard, F. & Soter, S. The contamination of Iapetus by Phoebe dust. Astron. Soc. Pacif. Conf. Ser. 104B, 179–182 (1996)

    ADS  Google Scholar 

  4. 4

    Porco, C. C. et al. Cassini imaging science: initial results on Phoebe and Iapetus. Science 307, 1237–1242 (2005)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Hamilton, D. P. Motion of dust in a planetary magnetosphere–orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn’s E ring. Icarus 101, 244–264 (1993)

    ADS  Article  Google Scholar 

  6. 6

    Cruikshank, D. P. et al. The dark side of Iapetus. Icarus 53, 90–104 (1983)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Buratti, B. J. & Mosher, J. A. The dark side of Iapetus: additional evidence for an exogenous origin. Icarus 115, 219–227 (1995)

    ADS  Article  Google Scholar 

  8. 8

    Vilas, F., Larsen, S. M., Stockstill, K. R. & Gaffey, M. J. Unraveling the zebra: clues to the Iapetus dark material composition. Icarus 124, 262–267 (1996)

    ADS  Article  Google Scholar 

  9. 9

    Jarvis, K. S., Vilas, F., Larsen, S. M. & Gaffey, M. J. Are Hyperion and Phoebe linked to Iapetus? Icarus 146, 125–132 (2000)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Buratti, B. J., Hicks, M. D., Tryka, K. A., Sittig, M. S. & Newburn, R. L. High resolution 0.33–0.92 μm spectra of Iapetus, Hyperion, Phoebe, Rhea, Dione, and D-type asteroids: How are they related? Icarus 155, 375–381 (2002)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Buratti, B. J., Hicks, M. D. & Davies, A. Spectrophotometry of the small satellites of Saturn and their relationship to Iapetus, Phoebe, and Hyperion. Icarus 175, 490–495 (2005)

    ADS  Article  Google Scholar 

  12. 12

    Cruikshank, D. P. et al. Hydrocarbons on Saturn’s satellites Iapetus and Phoebe. Icarus 193, 334–343 (2008)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Clark, R. N. et al. Compositional mapping of Saturn’s moon Phoebe with imaging spectroscopy. Nature 435, 66–69 (2005)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Nesvorný, D. Alvarellos, J. L. A., Dones, L. & Levison, H. F. Orbital and collisional evolution of the irregular satellites. Astron. J. 126, 398–429 (2003)

    ADS  Article  Google Scholar 

  15. 15

    Hamilton, D. P. &. Krüger, H. The sculpting of Jupiter’s gossamer rings by its shadow. Nature 453, 72–75 (2008)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Hamilton, D. P. The asymmetric time-variable rings of Mars. Icarus 119, 153–172 (1996)

    ADS  Article  Google Scholar 

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This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

Author Contributions All authors contributed substantially to this work. A.J.V. and M.F.S. did most of the observation planning, data reduction, and associated write-up. D.P.H. contributed most of the dynamical interpretations and write-up.

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Correspondence to Anne J. Verbiscer.

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Verbiscer, A., Skrutskie, M. & Hamilton, D. Saturn's largest ring. Nature 461, 1098–1100 (2009).

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