Voyager images reveal that three prominent clumps in Saturn's F ring were short-lived, appearing rapidly and then spreading and decaying in brightness over periods of similar to 2 weeks. These features arise from hypervelocity impacts by similar to 10-centimeter meteoroids into F ring bodies. Future ring observations of these impact events could constrain the centimeter-sized component of the meteoroid population, which is otherwise unmeasurable but plays an import ant role in the evolution of rings and surfaces in the outer solar system. The F ring's numerous other trumps are much longer lived and appear to be unrelated to impacts.