7677 20260127182541.0 CTALK-2026-0001 Rivoldini, Attilio Effect of Mercury's interior structure on its long-period libration 2025 2025-09-07 Mercury experiences long-period forced librations as a result of periodic gravitational perturbations on its orbit from other planetary bodies. These librations can be resonantly amplified when the planetary forcing periods are close to one of the two free libration normal modes. The periods of the free libration modes strongly dependent on the interior structure of the planet and on couplings between the solid shell, outer core, and inner core. Among the internal couplings, the gravitational-pressure coupling between the planet shell and inner core has the largest effect on the forced libration amplitude and free libration periods. Although dissipative couplings — of electromagnetic or viscous origin as well as the viscous relaxation of the inner core — have a small effect on the free libration periods, they can substantially affect the amplitude of the forced libration. In this study, we investigate the effect of Mercury's interior structure, composition, thermal state, and dynamical shape on the long-period librations, incorporating the effects of internal couplings. We compare our model predictions with the recently derived long-period libration time series obtained from co-registration of MESSENGER laser altimeter observations (Xiao et al. 2025, this meeting). NO Van Hoolst, Tim XIao, Haifeng Trinh, Antony Tosi, Nicola Yseboodt, Marie Baland, Rose-Marie Rekier, Jérémy Triana, Santiago Andres Briaud, Arthur EPSC-DPS Joint Meeting 2025 marie.yseboodt@ksb-orb.be 10.5194/epsc-dps2025-1543 1139330 http://publi2-as.oma.be/record/7677/files/EPSC 2025 Rivoldini.pdf 6088 http://publi2-as.oma.be/record/7677/files/EPSC 2025 Rivoldini.gif?subformat=icon icon 8200 http://publi2-as.oma.be/record/7677/files/EPSC 2025 Rivoldini.jpg?subformat=icon-180 icon-180 Contributed CTALKCONT