Physical collisions of moonlets and clumps with the Saturn's F-ring core

Since 2004, observations of Saturn's F-ring have revealed that the ring's Core is surrounded by structures with radial scales of hundreds of kilometers, called "spirals" and "jets." Gravitational scattering by nearby moons was suggested as a potential production mechanism: however, it remained doubtful because a population of Prometheus-mass moons is needed and. obviously, such a population does not exist in the F-ring region. We investigate here another mechanism: dissipative physical collisions of kilometer-size moonlets (or clumps) with the F-ring core. We show that it is a viable and efficient mechanism for producing spirals and jets, provided that massive moonlets are embedded in the F-ring core and that they are impacted by loose clumps Orbiting in the F-ring region, which could be consistent with recent data from ISS, VIMS and UVIS. We show also that coefficients of restitution as low as similar to 0.1 are needed to reproduce the radial extent of spirals and Jets, suggesting that collisions are very dissipative in the F-ring region. In conclusion, spirals and jets would be the direct manifestation the ongoing collisional activity of the F-ring region. (c) 2009 Elsevier Inc. All rights reserved.