Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.1102b&link_type=abstract
American Astronomical Society, DPS meeting #39, #11.02; Bulletin of the American Astronomical Society, Vol. 39, p.428
Astronomy and Astrophysics
Astronomy
Scientific paper
The heating mechanism that created the melting and global expansion necessary to form Ganymede's ubiquitous grooved terrains remains unclear. While the current Laplace resonance does not pump Ganymede's eccentricity, Malhotra (1991) and Showman and Malhotra (1997) showed that the Galilean satellites may have passed through Laplace-like resonances that did force Ganymede's eccentricity, leading to internal heating of the satellite. Showman et al. (1997) explored the effects of such tidal heating on Ganymede and found that it can lead to thermal runaway and melting, helping to explain the extensive resurfacing of the satellite. While the likelihood of thermal runaway appeared small, improved understanding of the internal structure of Ganymede and the nature of stagnant lid convection warrants a new study. Here we present simulations of Ganymede's coupled thermal and orbital evolution. The orbital model allows a dynamical investigation of the orbital histories of the Galilean satellites near the observed 2:1 mean motion resonance. The thermal model simultaneously solves the energy balance in Ganymede's ice shell, silicate mantle, and Fe/FeS core. Stagnant lid convection, radiogenic heating, ocean formation, and inner core growth are included in the model. Coupling between the orbital and thermal models occurs via tidal dissipation, which uses the model of Tobie et al. 2005 to determine how tidal heating is distributed throughout the satellite interior. These simulations reveal that passage through the Laplace-like resonance can lead to melting under a much broader range of initial conditions than suggested by Showman et al. (1997). Such melting requires that the grain sizes in Ganymede's icy mantle be 1 mm or less, and that the Galilean satellites passed through one of the stronger Laplace-like resonances. The generation of melt would not only lead to satellite expansion and extensional stress, but would also provide a source of near surface melt, permitting cryovolcanic activity.
Bland Michael T.
Showman Adam P.
Tobie Gabriel
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