Evolution of the Janus-Epimetheus coorbital resonance due to torques from Saturn's rings

The effects of the gravitational interactions between Saturn's rings and the coorbital satellites, Janus and Epimetheus, on the 1:1 horseshoe resonance between these moons is examined. It is shown that the 7:6 resonance of these moons, which presumably maintains the sharp outer edge of the A ring, leads to a rapid tightening of the coorbital lock. The results lead to the prediction that the orbital configuration might evolve from the current horseshoe-type lock to one of tadpole orbits around a single Lagrangian point in about 20 myr.