000006594 001__ 6594
000006594 005__ 20240122122212.0
000006594 037__ $$aCTALK-2024-0006
000006594 100__ $$aBaland, R.-M.
000006594 245__ $$aThe obliquity of Mercury: Models and interpretation (Invited)
000006594 260__ $$c2023
000006594 269__ $$c2023-07-06
000006594 520__ $$aMercury is locked in an unusual 3:2 spin-orbit resonance and as such is expected to be in a state of equilibrium called Cassini state. In that state, the angle between the spin axis and orbit normal, called obliquity, remains almost constant while the spin axis remains almost in the plane, also called Cassini plane,  defined by the normal to the Laplace plane and the normal to the orbital plane. The spin axis and the orbit normal precess together with a period of about 300 kyr. The orientation of the spin axis of Mercury has been estimated using different approaches: (i) Earth-based radar observations, (ii) Messenger images and altimeter data, and (iii) Messenger radio tracking data. The different estimates all tend to confirm that Mercury occupies the Cassini state. The  observed obliquity is small and close to 2 arcmin. It indicates a normalized polar moment of inertia of about 0.34. This information, combined with the existence of a liquid iron core, as evidenced by the librations, allows to constrain the interior structure of Mercury. However, the different estimates of the orientation of the spin axis locate the spin axis somewhat behind or ahead of the Cassini plane, and it is difficult to reconcile and interpret them coherently in terms of detailed interior properties. We will review recent models for the obliquity and spin orientation of Mercury, which include the effects of complex orbital dynamics, tidal deformations and associated dissipation, and internal couplings related to the presence of fluid and solid cores. Next, we will discuss the possible interpretations of the orientation estimates in term of interior properties.
000006594 536__ $$a3PRODPLANINT/$$c3PRODPLANINT/$$f3PRODPLANINT 
000006594 594__ $$aNO
000006594 6531_ $$aMercury
000006594 773__ $$tComplex Planetary Systems II Kavli-IAU Symposium 382, Namur, Belgium
000006594 8560_ $$frose-marie.baland@ksb-orb.be
000006594 85642 $$ahttps://cpsii.unamur.be/
000006594 906__ $$aInvited
000006594 980__ $$aCTALKINVI