The origin of planetary rings is not precicely known, but they are thought to be unstable and dissipate over the course of tens or hundreds of millions of years. As a result, modern ring systems must be of modern origin, possibly formed of debris from a moon that suffered a large impact or was disrupted by the parent planet's gravity when it passed within the [Roche limit]?.
The composition of ring particles varies, and can be either silicate or icy dust.