1. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 392 UCB, Boulder, Colorado 80309-0392, USA
2. Nonlinear Dynamics, Department of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany
3. Astronomy Division, Department of Physical Sciences, University of Oulu, 90014 Oulu, Finland

Correspondence to: Miodrag Sremevi¹ Correspondence and requests for materials should be addressed to M.S. (Email: miodrag.sremcevic@lasp.colorado.edu).

Abstract

The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences, with direct implications for planet-forming processes in pre-planetary disks¹. The recent detection of four propeller-shaped features in Saturn's A ring² proved the presence of large boulder-sized moonlets in the rings^{3, 4, 5}. Their existence favours ring creation in a catastrophic disruption of an icy satellite rather than a co-genetic origin with Saturn, because bodies of this size are unlikely to have accreted inside the rings. Here we report the detection of eight new propeller features in an image sequence that covers the complete A ring, indicating embedded moonlets with radii between 30 m and 70 m. We show that the moonlets found are concentrated in a narrow 3,000-km-wide annulus 130,000 km from Saturn. Compared to the main population of ring particles^{6, 7, 8} (radius s < 10 m), such embedded moonlets have a short lifetime⁹ with respect to meteoroid impacts. Therefore, they are probably the remnants of a shattered ring-moon of Pan size or larger², locally contributing new material to the older ring. This supports the theory of catastrophic ring creation in a collisional cascade^{9, 10, 11, 12}.

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