Diffuse Rings

  • M. Horányi
  • J. A. Burns
  • M. M. Hedman
  • G. H. Jones
  • S. Kempf


In order to give context to Cassini's findings about Saturn's diffuse rings, this chapter first recalls the Vo y a g e r and telescopic observations prior to 2004. Cassini has investigated these faint rings composed of small particles with remote sensing (visual and infrared imaging) and in-situ detectors (charged-particle and dust detectors), for the first time allowing results obtained by the different techniques to be compared. Generally the agreement is good. The description of the observations are organized by increasing distance from Saturn, and includes (a) the faint rings in and around the main rings; (b) spokes in the B-ring; (c) the narrow outer faint rings; (d) the E-ring with emphasis on its connection to Enceladus's geysers; and (e) the Saturnian dust streams. These discussions also summarize relevant models that have been proposed to explain the behavior of charged dust grains. Except for the spokes and much of the E ring, the particles in these rings are collisional debris. Saturn's D ring has changed significantly since Voyager; part of it seems to be inclined and winding up while another portion (and the Roche Division) has periodic structures that are forced by Saturn's magnetic field. The faint rings in ring gaps are also time-variable and some have Sun-aligned elliptical orbits. The reappearance of the enigmatic spokes should allow several recent theories to be tested. Rings and arcs have been discovered to accompany Cassini-found small moons that are trapped in satellite resonances. The realization that Enceladus feeds the E ring and the opportunity to make in-situ measurements, including the electric charge and composition of grains, has made this a rich topic. The dust streams are composed of nanoscale particles moving at speeds of many tens to hundreds of km s−2; they likely originate in the outer reaches of the E ring.


Dusty Plasma Hubble Space Telescope Solar Radiation Pressure Main Ring Ring Particle 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



All authors appreciate the efforts of Cassini's e n -gineers in providing an exceptional mission. MH thanks Antal Juhász for years of fruitful collaboration. JAB recognizes the contributions of numerous former graduate students on ethereal ring problems. JAB, MH and MMH have received support from NASA, the Cassini-Huygens Project and CDAP. GHJ holds an STFC Advanced Fellowship. SK acknowledges support from DLR.


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • M. Horányi
    • 1
  • J. A. Burns
    • 2
    • 3
  • M. M. Hedman
    • 2
  • G. H. Jones
    • 4
    • 5
  • S. Kempf
    • 6
  1. 1.Laboratory for Atmospheric and Space Physics, and Department of PhysicsUniversity of ColoradoBoulderUSA
  2. 2.Department of AstronomyCornell UniversityIthacaUSA
  3. 3.Department of Theoretical and Applied MechanicsCornell UniversityIthacaUSA
  4. 4.Mullard Space Science LaboratoryUniversity College LondonDorkingUK
  5. 5.The Centre for Planetary Sciences at UCL/BirkbeckLondonUK
  6. 6.Max Planck Institute for Nuclear PhysicsHeidelbergGermany

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