Despite all the new data, the nature of planetary rings is stíII
controversial. We don't know why each planetary ring is so different from the others and we have no idea of the nature of a single partícle ring, The large number of structures observed in planetary rings seems to indicate that many different physícal mechanisms are simultaneously at work. We are not yet able to include all of them in a single model. Resonances with nearby satellites play an ímportant role, but through complex mechanisms. Appropriate observations and more sophísticated models are needed to improve our understanding of rings and to identify the main physícal mechanisms involved.