Geodesy and geophysics of Mercury: prospects in view of the BepiColombo mission

Abstract

The BepiColombo mission, which is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), was launched successfully on October 20, 2018 from Kourou, French Guyana. The spacecraft is currently on its 7 yr cruise to Mercury. The main science campaign at Mercury will begin, however, no earlier than spring 2026, after two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO) have been inserted in their final orbits in late 2025. Mercury is an intriguing planetary object with respect to its dynamical state and evolution. The planet is differentiated and contains a large iron core overlain by a relatively thin silicate mantle and crust. Mercury is locked in a unique 3:2 spin-orbit coupling and its intrinsic magnetic dipole field shows that at least part of Mercury’s iron core is liquid. From libration measurements it has been concluded that Mercury’s outer core is liquid, decoupling the silicate mantle from the deep interior. Phases of global contraction and phases of volcanic activity are evidence for an eventful thermal evolution of the planet. In this paper the current knowledge on the evolution of Mercury, focusing on its dynamical, rotational and orbital state is summarized. Prospects for investigations with BepiColombo will be discussed.