Regensburg 2007 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 13: Cassini bei Saturn

EP 13.3: Talk

Thursday, March 29, 2007, 14:15–14:30, H46

Dynamics of Enceladus' plume particles — •Uwe Beckmann, Sascha Kempf, Ralf Srama, Georg Moragas-Klostermeyer, Stefan Helfert, and Eberhard Grün — Max-Planck-Institut für Kernphysik, Heidelberg, Deutschland

Since July 1st 2004, the Cassini spacecraft has been exploring the Saturnian system, which is distinguished by a pronounced ring system. Knowledge of the dynamical properties of the ring particles is essential for understanding the ring formation. The Cosmic Dust Analyser (CDA) on Cassini measures the mass, speed, charge, and elemental composition of individual dust particles hitting the detector. On July 14th 2005, Cassini performed a close encounter at the icy moon Enceladus - the dominant E ring dust source. The CDA data obtained during this flyby can only be explained by a collimated dust source at the south pole area of the moon. This finding finally led to the discovery of a strong cryo-volcanism in this region replenishing the ring with fresh dust.

Here, we present model calculations for dust grains ejected at Enceladus' south pole into the ring. We show that only grains 14 m/s faster than the moon's three-body escape speed do not re-collide with Enceladus during their first orbit and thus be able to populate the ring. Our numerical results match the CDA data reasonably well. In particular, our findings explain the vertical extent of the ring as derived from the in-situ observations.