The Source of Saturn's G Ring
Matthew M. Hedman,1*
Joseph A. Burns,1,2
Matthew S. Tiscareno,1
Carolyn C. Porco,3
Geraint H. Jones,4,5
Elias Roussos,4
Norbert Krupp,4
Chris Paranicas,6
Sascha Kempf7
The origin of Saturn's narrow G ring has been unclear. We show that it contains a bright arc located 167,495.6 ± 1.3 km from Saturn's center. This longitudinally localized material is trapped in a 7:6 corotation eccentricity resonance with the satellite Mimas. The cameras aboard the Cassini spacecraft mainly observe small (1 to 10 micrometers) dust grains in this region, but a sharp decrease in the flux of energetic electrons measured near this arc requires that it also contain larger (centimeter- to meter-sized) bodies whose total mass is equivalent to that of a 
100-meter-wide ice-rich moonlet. Collisions into these bodies may generate dust, which subsequently drifts outward to populate the rest of the G ring. Thus, the entire G ring could be derived from an arc of debris held in a resonance with Mimas.
1 Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
2 Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, NY 14853, USA.
3 Cassini Imaging Central Laboratory for Operations, Space Science Institute, Boulder, CO 94043, USA.
4 Max Planck Institut für Sonnensystemforschung, Katlenburg-Lindau 37191, Germany.
5 Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK.
6 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA.
7 Max Planck Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
* To whom correspondence should be addressed. E-mail: mmhedman{at}astro.cornell.edu
