Internal Structure and Dynamics of the Galilean Satellites
Francis Nimmo (University of California)
Anton Ermakov (Stanford University)
Wanying Kang (Massachusetts Institute of Technology)
Marc Rovira-Navarro (TU Delft - Aerospace Engineering)
Gabriel Tobie (Le Mans Université, Le Mans, Universite d’Angers, Centre National de la Recherche Scientifique (CNRS), Université de Nantes)
Tim Van Hoolst (Katholieke Universiteit Leuven, Royal Observatory of Belgium)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
We review the key observations and theories relevant to the internal structure and dynamics of the Galilean satellites. Key observations include: the bulk densities and degree-two gravity coefficients of the moons; the presence of conductive subsurface layers, as inferred from magnetic induction; and the surface compositions. All the moons, with the possible exception of Callisto, appear to be differentiated (denser components have separated from lighter components). Ganymede and Io have iron cores; Europa may have one. The outer three moons all likely possess subsurface oceans; for Europa the ocean overlies rock, while for the other two it overlies higher-pressure ice phases. Io is partially molten but does not possess a shallow magma ocean. Tidal heating is the dominant energy source at Europa and Io, and may have affected Ganymede’s long-term evolution. The dynamics of the subsurface oceans are of considerable theoretical interest but are only weakly tied to current or likely future observations. We identify seven outstanding questions regarding internal structures, some of which will be answered by the forthcoming JUICE, Europa Clipper and Tianwen-4 missions.
help_outline