The large obliquity of Saturn explained by the fast migration of Titan

The obliquity of a planet is the tilt between its equator and orbital plane. Giant planets are expected to form with near-zero obliquities. After formation, some dynamical mechanism must therefore have tilted Saturn up current 26.7{\deg}. This event traditionally thought happened more than 4 Gyrs ago during late planetary migration because crossing resonance spin-axis precession nodal mode Neptune. Here, we show that fast tidal Titan measured by Lainey et al. (2020) incompatible this scenario, it offers new explanation for Saturn's obliquity. A significant would prevent any early resonance, invalidating previous constraints on set tilting Saturn. We propose instead was encountered recently, about 1 Gyr ago, forcing increase from small value (possibly less 3{\deg}), state. scenario suggests normalised polar moment inertia lies 0.224 0.237. Our findings bring out paradigm evolution Saturn, Jupiter, possibly giant exoplanets in multiple systems, whereby obliquities not settled once all, but continuously evolve as result their satellites.