Titan’s outward tidal migration should be extremely slow because it orbits far from Saturn.

Moons can slowly move away from their planets because of tides.

A moon’s gravity raises a tidal bulge on its planet. If the planet rotates faster than the moon orbits, that bulge is carried slightly ahead of the moon and transfers angular momentum to it. The moon gains orbital energy and moves outward.

Older tidal models made this effect weaken very strongly with distance. Titan orbits far from Saturn, so its outward migration was expected to be extremely slow.

Cassini made the motion measurable.

Researchers used two independent approaches: decades of precise measurements of Titan’s position in the sky, and radio tracking of the Cassini spacecraft during close encounters. Both showed Titan moving outward much faster than expected—more than 100 times faster than many conventional estimates.

A leading explanation is resonance locking.

Saturn can vibrate internally in many natural patterns, or oscillation modes. As the planet slowly changes over time, the frequencies of these modes also change. Under the right conditions, Titan’s orbital motion can stay locked to one of them, maintaining a strong tidal interaction even at a large distance.

The faster migration changes reconstructions of Saturn’s moon system because Titan and other moons may have moved much farther over time than older models allowed.

Distance still matters to tidal physics. The correction is that distance alone does not determine the migration rate around an evolving giant planet.