Saturn's ring rain

摘要

The origin and evolution of Saturn's rings has been a particularly vexing problem over the past several decades of planetary exploration, and is one that has obvious implications for the formation of the Solar System. And although much progress has been made in understanding the dynamics of the ring system, both observationally and theoretically, the big questions remain unanswered. How and when did Saturn's rings form? Can they be the last surviving remnants of a much more massive ring system that formed 4.5 billion years ago1, coeval with the primordial gaseous disk that condensed to form Saturn?