Signature of Mercury's core on its librations

HR: 1340h
AN: G43A-0792 [Abstracts]
TI: Signature of Mercury's core on its librations
AU: * Rambaux, N
EM: Nicolas.Rambaux@oma.be
AF: Royal Observatory of Belgium, 3, avenue circulaire, Brussels, 1180 Belgium
AU: Dehant, V
EM: Veronique.Dehant@oma.be
AF: Royal Observatory of Belgium, 3, avenue circulaire, Brussels, 1180 Belgium
AU: Van Hoolst, T
EM: timvh@oma.be
AF: Royal Observatory of Belgium, 3, avenue circulaire, Brussels, 1180 Belgium
AU: Bois, E
EM: eric.bois@obs-nice.fr
AF: Observatoire de la C\^ote d'Azur, Boulevard de l'Observatoire, Nice, F-06304 France
AB: The internal structure of Mercury is the most puzzling among the terrestrial planets. The space missions MESSENGER and the upcoming BepiColombo, and ground-based radar measurements will play an important role in constraining our understanding of the structure, formation, and evolution of Mercury. The development of a complete theory of the coupled spin-orbit motion of Mercury within the Solar System is an essential complement to observational data and will improve significantly our knowledge of the planet. In order to integrate hermean core-mantle interaction in a realistic model of the Mercury's rotation, we have used the SONYR model of the solar System including Mercury's spin-orbit motion (acronym of Spin-Orbit N-bodY Relativistic model). We studied the dynamical behavior of the rotational motion of Mercury considered as a homogeneous body and as a model with two layers. The comparison of the dynamical evolution of the models of internal structure permits to clarify the impact of the core motion on the librations. The libration amplitude is not proportional to the $C_m/C$ ratio because of the non-linearity of the effect of the core-mantle interaction on the rotation. Moreover, we have computed the impact of the presence of the core on the spin rate of the planet in order to compare with recent radar observations.
DE: 5430 Interiors (8147)
DE: 5450 Orbital and rotational dynamics
DE: 6235 Mercury
DE: 1239 Rotational variations
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting