2007/09/07 by E. Bois, Nicolas Rambaux, N. Rambaux
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Angular momentum #Astro and Planetary Science #Astrobiology #Astronomy #Astrophysics #Celestial mechanics #Classical mechanics #Ephemeris #Geomagnetism and Paleomagnetism Studies #Geometry #Libration (molecule) #Mercury (programming language) #Orbital elements #Orbital motion #Orbital plane #Physics #Planet #Planetary Science and Exploration #Satellite #Solar System #astro-ph
paper · pdf · doi:10.1016/j.icarus.2007.07.015
published as Icarus 192 (2007) 308-317 · 30 pages, 3 tables, 8 figures, accepted to Icarus (26 Jul 2007)
arxiv created 2007/09/07 · openalex publication_date 2007/09/08 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
One major objective of MESSENGER and BepiColombo spatial missions is to accurately measure Mercury's rotation and its obliquity in order to obtain constraints on internal structure of the planet. Which is the obliquity's dynamical behavior deriving from a complete spin-orbit motion of Mercury simultaneously integrated with planetary interactions? We have used our SONYR model integrating the spin-orbit N-body problem applied to the solar System (Sun and planets). For lack of current accurate observations or ephemerides of Mercury's rotation, and therefore for lack of valid initial conditions for a numerical integration, we have built an original method for finding the libration center of the spin-orbit system and, as a consequence, for avoiding arbitrary amplitudes in librations of the spin-orbit motion as well as in Mercury's obliquity. The method has been carried out in two cases: (1) the spin-orbit motion of Mercury in the 2-body problem case (Sun-Mercury) where an uniform precession of the Keplerian orbital plane is kinematically added at a fixed inclination (S2K case), (2) the spin-orbit motion of Mercury in the N-body problem case (Sun and planets) (Sn case). We find that the remaining amplitude of the oscillations in the Sn case is one order of magnitude larger than in the S2K case, namely 4 versus 0.4 arcseconds (peak-to-peak). The mean obliquity is also larger, namely 1.98 versus 1.80 arcminutes, for a difference of 10.8 arcseconds. These theoretical results are in a good agreement with recent radar observations but it is not excluded that it should be possible to push farther the convergence process by drawing nearer still more precisely to the libration center.