![]() Durisen & Estrada ( 2023) showed that the process of direct deposition of micrometeoroids and the ballistic transport of their impact ejecta can account for these mass-loss rates, and Estrada & Durisen ( 2023) used these results to demonstrate that mass loading and ballistic transport due to micrometeoroid bombardment continue to drive the rings' dynamical evolution once viscosity becomes too weak. ![]() 2019), suggesting they are not only young but ephemeral as well. Moreover, the rings appear to be losing mass at a remarkable rate (Hsu et al. The present mass of the main rings is ∼0.4 Mimas masses (∼1.5 × 10 19 kg). 2017a, 2017b) are continuously subjected to micrometeoroid bombardment and are darkened over time, so an upper bound on the rings' exposure age can be determined by assuming that they began as pure ice (Cuzzi & Estrada 1998 Estrada et al. This is because the primarily icy rings (>95% by mass, Doyle et al. Together, these three factors constrain the ring age to be less than a few hundred megayears (Estrada et al. 2017a, 2017b), and the extrinsic micrometeoroid flux at Saturn (Kempf et al. 2019), the fraction of non-icy material in the rings (Zhang et al. ![]() Key observations made during the Cassini mission provided new measurements of the ring mass (Iess et al. Whatever their origin, Saturn's rings appear to be young. This could prompt further disruption and facilitate a collisional cascade to distribute more debris for potential ring formation, the re-formation of the present-day moons, and evolution into an eventual cratering population of planetocentric impactors. In addition, fragments and debris of rock and ice totaling more than the mass of Enceladus can be placed onto highly eccentric orbits that would intersect with any precursor moons orbiting in the vicinity of Mimas, Enceladus, or Tethys. This includes the direct placement of pure-ice ejecta onto orbits that enter Saturn's Roche limit, which could form or rejuvenate rings. Using high-resolution smoothed particle hydrodynamics simulations, we find that this kind of impact can produce a wide distribution of massive objects and scatter material throughout the system. Such an event could have been triggered a few hundred million years ago by resonant instabilities in a previous satellite system. We simulate the collision of precursor icy moons analogous to Dione and Rhea as a possible origin for Saturn's remarkably young rings.
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