Particle Porosity and the Search for Saturn’s Ring Roomba

At the end of Cassini's fourteen year tour of the Saturn system we have discovered many things about the rings-- but remarkably, the age of the ring system is still in debate. Whereas a formation early in the solar system seems more likely, two items widely thought to imply young rings are their supposed dynamical instability, and the fact that they are relative pristine. Charnoz has recently presented a compelling dynamical argument suggesting that old, massive, rings might be in fact expected to asymptotically approach something similar to what we observe today. That leaves the question of ring purity. I'll discuss a potential mechanism by which ejecta may be swept away as they are created by meteoroid impacts on the rings. If such a 'ring roomba' is at play, it might explain the large amounts of material observed inside the rings during Cassini's final orbits, as well as explain how an ancient ring system could still look clean today. A small part of this picture hinges on ring particle porosity, which Ferrari and Pilorz have been examining via the rings' thermal responses.