Geodesy and Geophysics Working Group

Primary Questions

  • What is the thickness and density of the crust?

  • What has shaped the surface of Mercury?

  • What are the relative roles of tectonism, volcanism and impacts with respect to Mercury’s surface?

  • How strong was the contraction and when did it occur?

  • What are the regions in the southern hemisphere that present crustal magnetization?

  • What is the structure and rheology (i.e, viscosity, rigidity) of the mantle?

  • What is the size, density and physical state (liquid, solid) of the core?

  • What is the relative amount of volatiles in the core?

  • What is Mercury’s deviation from hydrostatic state?

  • What is the level of precision of Einstein’s theory of General Relativity?

  • Are any violations of the Strong Equivalence Principle (SEP) in the weak-field?

  • How does the solar inter- nal evolution affect planetary ephemerides?

  • How and when did Mercury get captured in the 3:2 spin-orbit resonance?

Science Objectives

  • Local and global mapping of gravity and topographic relief
  • Local and global measurements of the magnetic field
  • Accurate global determination of Mercury’s degree 2 shape and gravity
  • Gravitational and surface tides measured by the Love numbers k2 and h2, including phase lags.
  • Polar moment of inertia of the outer layers (crust and mantle) by measuring librations with altimetric data.

  • Internal magnetic field magnitude and structure (i.e., dipole and equatorial offset)

  • Accurate measure of the offset between the center of mass and the center of figure

  • Mercury rotation from altimetry and orbital period from radio science

  • Parameterized PostNewtonian (PPN) γ, β,  α1, and α2. Nordvedt's parameter η.

  • Sun’s J2, and GM and its temporal variation due to solar mass loss rate.

Meetings (most recent first)

Virtual Meetings: 

1st GGWG virtual meeting on Friday 18 June. Two science talks: 

and final discussion.


2nd GGWG virtual meeting on Friday 24 September. Two science talks: 

and final discussion.


3rd GGWG virtual meeting on Friday 26 November. Two science talks: 

and final discussion.


4th GGWG virtual meeting on Friday 21 January 2022. Two science talks: 

  • Agnes Fienga, "INPOP Planetary Ephemerides and BepiColombo : from Orbit Improvements to GR and Alternative Theories tests"

  • Clifford M. Will, "Zombie Alert!  Solar System Tests of General Relativity are Still Alive"

and final discussion.


5th GGWG virtual meeting on Friday 25 March 2022. Two science talks: 

and final discussion.


6th GGWG virtual meeting on Friday 17 June 2022. One science talk: 

and final discussion.


GGWG meeting on July 11 June 2022 with the following agenda: 

  • 2:00-2:20pm BELA report + 10-min discussion
  • 2:30-2:50pm ISA report + 10-min discussion
  • 3:00-3:20pm MORE report + 10-min discussion
  • 3:30-3:50pm MPO-MAG report + 10-min discussion
  • 4:00-5:00pm Short presentations on the first results with Venus and Mercury flybys


7th GGWG virtual meeting on Friday 24 March 2023. The science talk: 

and final discussion.


8th GGWG virtual meeting on Friday 9 June 2023. The meeting is focused on: 

  • BepiColombo Perihelion Science Strategy

  • TMX

and final discussion.



  • Next GGWG virtual meeting will be on September 24.

Working Group Chair

  • Hauke Hussmann
  • Antonio Genova

Other Information