what do the large moons/planets get zapped by to make the rocks around saturn?

Question: what do the large moons/planets get zapped by to make the rocks around saturn?
- Keywords:
  planet,
  saturn,
  space,
  space debri
Asked by tararowanx to Hitesh, Hywel, Mae, Nik, Tiffany on 13 Jun 2012.
- Tiffany Taylor answered on 13 Jun 2012:
  
  I just wikipedia’d it. They say an asteroid shower might have broken up a nearby moon about 4 billion years ago. So the rings are not contently being added to, they are from an event which happened a really long time ago and have stuck.

Question: what do the large moons/planets get zapped by to make the rocks around saturn?