The Orbital History of Mimas, Enceladus and Dione

We numerically study the past tidal evolution of Mimas, Enceladus and Dione. We investigate a novel scenario explaining the role of Dione in a possible mutual past resonance between Mimas and Enceladus. We investigate this configuration by hypothesizing that a "resonance handoff" occurred between the Mimas-Enceladus, with Mimas migrating away, and Enceladus and Dione remaining in resonance. We find that Mimas would affect the Enceladus-Dione MMR by i) creating orbital overlap of resonances, during which the eccentricity of Mimas is excited to its current value, ii) pushing Enceladus outward faster and thus contributing to its capture into the present MMR. Our model can explain the time scale of less than 100 Myr for capture of Enceladus into MMR with Dione, despite their slow orbital convergence.