>
> A further example of my previous discussion points:
>
> Observatoire de Paris
> Paris, France
>
> 6 May 2008
>
> The Mystery of Titan's Rotation
>
> Usually, the tidal effects applied by the parent planet on their natural
> satellites are strong enough to slow down their spin velocities and lock
> them in a synchronous rotation. As a consequence, the satellite always
> shows the same side to its planet, as it is the case for the Moon. Cassini
> spacecraft has recently observed a super-synchronous rotation for Titan,
> and several hypotheses are introduced to explain this observation. Some
> astronomers of IMCCE (Paris Observatory) are part of a team who suggests
> that the spin rate measurements might be altered.
>
> Due to tidal effects, the rotation of the natural satellites is expected
> to be synchronous with their revolution, i.e. they perform a whole
> rotation during a complete revolution around their parent planet. It
> corresponds to a dynamical equilibrium state, that involves that the
> satellite always shows the same side to its planet.
>
> Cassini spacecraft has recently observed a slight super-synchronous
> rotation of Titan (+0.004%%) and the authors interpret it as a signature of
> an internal ocean, that would dissociate the rotation of Titan's crust
> from this of the core, justified by the fact that the motion of the crust
> would be sensitive to the energy exchanges with the atmosphere.
>
> Another explanation is being proposed by researchers of the University of
> Namur (Belgium), the University of Lille 1 and Paris Observatory (IMCCE).
> Following Benoit Noyelles, Anne Lemaitre and Alain Vienne, there could be
> a dynamical forcing of the angle (the wobble) between Titan's rotation and
> pole axes, that could false the measurement of Titan's spin rate if these
> axes were considered as equal.
>
> Cassini space mission has been extended for at least two years, so more
> accurate measurements would allow to confirm or refine these explanations.
>
> References
>
> Lorenz R., Stiles B., Kirk R. et al., 2008, "Titan's Rotation Reveals an
> Internal Ocean and Changing Zonal Winds", Science, 319, 1649
>
> Noyelles B., Lemaitre A. & Vienne A., 2008, "Titan's rotation: A
> 3-dimensional theory", Astron. Astrophys., 478, 959-970
>
> Noyelles B., 2008, "Titan's rotational state: The effects of a forced
> "free"
> resonant wobble", Cel. Mech. Dyn. Astr., in press, arXiv:0709.2293