Typical long-term evolution of the semi-major axes (Δa and a). The bottom graphs also show the pericenter and apocenter distances, represented as a colored interval around the value of a. Left column: stable case where, after the first capture of Callisto into resonance, the system remains in the same configuration and the migration of the satellites is almost linear. Right column: unstable case where, at about 3.5 Gyr after time J2000, one of the resonances is disrupted and a new one is formed.