Geodesy, Geophysics and Fundamental Physics Investigations of the BepiColombo Mission

Abstract

In preparation for the ESA/JAXA BepiColombo mission to Mercury, thematic working groups had been established for coordinating the activities within the BepiColombo Science Working Team in specific fields. Here we describe the scientific goals of the Geodesy and Geophysics Working Group (GGWG) that aims at addressing fundamental questions regarding Mercury’s internal structure and evolution. This multidisciplinary investigation will also test the gravity laws by using the planet Mercury as a proof mass. The instruments on the Mercury Planetary Orbiter (MPO), which are devoted to accomplishing the GGWG science objectives, include the BepiColombo Laser Altimeter (BELA), the Mercury orbiter radio science experiment (MORE), and the MPO magnetometer (MPO-MAG). The onboard Italian spring accelerometer (ISA) will greatly aid the orbit reconstruction needed by the gravity investigation and laser altimetry. We report the current knowledge on the geophysics, geodesy, and evolution of Mercury after the successful NASA mission MESSENGER and set the prospects for the BepiColombo science investigations based on the latest findings on Mercury’s interior. The MPO spacecraft of the BepiColombo mission will provide extremely accurate measurements of Mercury’s topography, gravity, and magnetic field, extending and improving MESSENGER data coverage, in particular in the southern hemisphere. Furthermore, the dual-spacecraft configuration of the BepiColombo mission with the Mio spacecraft at higher altitudes than the MPO spacecraft will be fundamental for decoupling the internal and external contributions of Mercury’s magnetic field. Thanks to the synergy between the geophysical instrument suite and to the complementary instruments dedicated to the investigations on Mercury’s surface, composition, and environment, the BepiColombo mission is poised to advance our understanding of the interior and evolution of the innermost planet of the solar system.

The BepiColombo Planetary Magnetometer MPO-MAG: What Can We Learn from the Hermean Magnetic Field?

“…To better understand Mercury's internal structure, geodetic measurements, e.g. the planet's obliquity and libration, provide a significant constraint for the interior models, since they are strongly connected to the radial density variations and the physical state (solid or liquid) of the single layers (see Genova et al (2021), in this issue). Additionally, equations of state describing the behavior of the constituent materials are also needed for interior modelling.…”

Interiors of Earth-Like Planets and Satellites of the Solar System

“…This complements recent high-pressure experiments on relevant core compositions and theoretical modeling of the planet's thermal evolution, mantle dynamics and core dynamo. Detailed reviews of results from the MESSENGER mission and the implications for the planet's interior can be found in Margot et al (2018), Johnson et al (2018), andHauck et al (2018), see also Genova et al (2021).…”

Evaluation of Recent Measurements of Mercury’s Moments of Inertia and Tides Using a Comprehensive Markov Chain Monte Carlo Method

“…Their value is higher than what our modeling predicts, although our value of 1.02 ± 0.04 is within their onesigma bound. Future analysis using laser altimetry from the BepiColombo mission to Mercury may provide improved h 2 measurements (Steinbrügge et al 2018b;Thor et al 2020;Genova et al 2021;Thomas et al 2021), against which our predicted value can be tested. Alternatively, an estimate of h 2 can then serve as an additional measurement to better constrain the properties of Mercury's inner core (Steinbrügge et al 2018a).…”

“…Additional and combined analysis of both MESSENGER gravity and altimetry may further address this, but that is outside the scope of this analysis. Future data from the BepiColombo mission to Mercury will greatly benefit studies of the planet's interior, by providing improved and additional constraints on the deep interior (e.g., Steinbrügge et al 2018a;Genova et al 2021).…”