Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
EPSC Abstracts
Vol. 15, EPSC2021-621, 2021
Europlanet Science Congress 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

The rotation of Ganymede and Callisto

Tim Van Hoolst1,2, Rose-Marie Baland1, Mikael Beuthe1, Alexis Coyette3, Attilio Rivoldini1, and Marie Yseboodt1
Tim Van Hoolst et al.
  • 1Royal Observatory of Belgium, Reference Systems and Planetology, Brussels, Belgium (
  • 2Institute of Astronomy, KU Leuven, Leuven, Belgium
  • 3University of Namur, Department of Mathematics, Namur, Belgium

The rotation rates of Ganymede and Callisto, the two largest satellites of Jupiter, are on average equal to their orbital mean motion but cannot be constant as a result of the varying gravitational torque exerted by Jupiter on the satellites. For a Keplerian orbit, the period of the torque and of the rotation variations is equal to the orbital period. Gravitational interaction with the other Galilean satellites and the Sun induces deviations from a purely Keplerian orbital motion, leading to changes in the gravitational torque of Jupiter on the satellites with respect to the mean Keplerian orbital motion and therefore to additional rotation variations. Here we discuss small variations from the average rotation on different time scales and assess the potential of using rotation as a probe of the interior structure.

The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation and tides of Ganymede and Callisto in the early 30s, and will in particular very accurately determine those quantities for Ganymede during the orbital phase of the spacecraft around that satellite starting in 2032. We report on different theoretical aspects of the rotation for realistic models of the interior of the satellites, include tidal deformations and take into account the low-degree gravity field and topography of Ganymede and Callisto. We assess the advantages of a joint use of rotation and tides to constrain the satellite's interior structure, in particular its ice shell and ocean.

How to cite: Van Hoolst, T., Baland, R.-M., Beuthe, M., Coyette, A., Rivoldini, A., and Yseboodt, M.: The rotation of Ganymede and Callisto, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-621,, 2021.

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