  Callisto is thought to possess a subsurface ocean, which will dissipate
energy due to obliquity tides. This dissipation should have damped any
primordial inclination within 1 Gyr - and yet Callisto retains a present-day
inclination. We argue that Callisto's inclination and eccentricity were both
excited in the relatively recent past (~0.3 Gyr). This excitation occurred as
Callisto migrated outwards according to the "resonance-locking" model and
passed through a 2:1 mean-motion resonance with Ganymede. Ganymede's orbital
elements were likewise excited by the same event. To explain the present-day
orbital elements we deduce a solid-body tidal k2/Q~0.05 for Callisto and a
significantly lower value for Ganymede.
