Letter | Published:

Width of a planetary ring system and the C-ring of Saturn

Nature volume 274, pages 669670 (17 August 1978) | Download Citation



PLANETARY ring systems such as those of Saturn and Uranus seem to have an inner limit analogous to the Roche outer limit. The analysis of the C-ring of Saturn described here gives an insight into its structure and dynamics. The quasi-steady distribution of particle sizes in a ring requires that besides collisional comminution and sputtering by protons, electrons and meteorites1 there are processes which permit the particles to grow. On Saturn, one of these processes is condensation2 on to the inner rings of water molecules sputtered from the outer edge3 of ring A. Another is the adhesion of smaller particles to the larger ones after low velocity collisions produced by gravitational attraction and by the differences in Keplerian velocities4. This process can include ejecta formed during cratering. The question arises under what condition these small particles will stay long enough on the surface of the larger ones to develop a permanent bond.

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  1. 1.

    & Astr. J. 75, 195 (1970).

  2. 2.

    Science (in the press).

  3. 3.

    & Bull. Am. astr. Soc. 9, 550 (1977); J. geophys. Res. (in the press).

  4. 4.

    , , & Icarus 30, 769 (1977).

  5. 5.

    Space Sci. Rev. 18, 3 (1975).

  6. 6.

    Icarus 22, 159 (1974).

  7. 7.

    Air Force Cambridge Rep. AFCRL-64-970 N65-22451 (1964).

  8. 8.

    Adv. Coll. Interf. Sci. 1, 111 (1967).

  9. 9.

    , & Nature 264, 344 (1976).

  10. 10.

    Commnt. Astrophys. (in the press).

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  1. Departments of Astronomy and Physics, University of Texas, Austin, Texas 78712



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