Discovery of an Arc of Particles near Enceladus' Orbit: A Possible Key to the Origin of the E Ring

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 1998-11, Vol.136 (1), p.50-59
• Main Authors: Roddier, C., Roddier, F., Graves, J.E., Northcott, M.J.
• Format: Article
• Language: English
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1006/icar.1998.6014

High angular resolution (adaptive optics) images taken on August 12, 1995 between 11:26 and 12:23 (UT) show a faint elongated structure apparently moving away from Saturn. The structure is consistent with light scattered by an arc of particles on a Keplerian orbit close to that of Enceladus. The orbit is slightly inclined (1.8°), and the arc is 76° ahead of the satellite. It appears to be a transient phenomenon since the arc brightness decreased by almost a factor two during the observations, and no such structure was observed at the same orbital position two days before. A possible explanation is that a large block of ice previously ejected by Enceladus collided with ice fragments trapped on the satellite orbit near its L4Lagrange point. The collision likely occurred about 6 h before observations started and produced a rapidly expanding cloud of small particles. We estimate the total mass of particles to be at least 105kg.