The Tidal-Thermal Evolution of the Pluto-Charon System

Cross-sections of plausible interior structure models for Charon (a) and Pluto (b). In (a) and (b), the thicknesses of the silicate parts (and therefore also of the ice layers) range from 395–430 km for Charon and 820– 890 km for Pluto, respectively, to keep the mean densities (Table 1) of the bodies fixed. Attenuation values (Q) are also indicated for the various layers. (c) illustrates the location of the main heat sources that are considered in this study, while arrows indicate the direction of the heat flow.

Existence of subsurface oceans on the satellites of the giant planets and Trans-Neptunian objects has been predicted for some time.

Oceans on icy worlds exert a considerable influence on the dynamics of the ice-ocean system and, because of the astrobiological potential, represent an important objective for future missions. The Pluto-Charon system is representative of an icy moon orbiting a dwarf planet formed from the remnants of a giant impact. Evolution of icy moons is primarily controlled by the mode and efficiency of heat transfer through the outer ice shell, which is influenced by the presence of impurities, by tidal dissipation in the ice shell, and the radioactive element budget in the core.

Previous studies on the evolution of the Pluto-Charon system considered either only the thermal or the tidal evolution, and in the cases where both were considered, the important effect of the presence of impurities in the liquid oceans was not addressed. We consider the joint tidal-thermal evolution of the system by combining a comprehensive tidal model that incorporates a viscoelastic tidal response with a parameterized convection model developed for icy worlds.

This approach enables an extensive analysis of the conditions required for formation and maintenance of subsurface liquid oceans to the present. Our results show that because of fast circularization and synchronization of the orbits, tidal heating is only important during the early stages of evolution (<1 Myr). We test the sensitivity of our results to the initial orbital and thermal parameters.

In all the cases, oceans on Pluto are always predicted to remain liquid to the present, ranging from 40 km to 150-km thick, whereas oceans on Charon have solidified. This is supported by New Horizons observations of extensional faults on Pluto and both extensional and compressional faults on Charon.

Amirhossein Bagheri, Amir Khan, Frederic Deschamps, Henri Samuel, Mikhail Kruglyakov, Domenico Giardini

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2109.13206 [astro-ph.EP] (or arXiv:2109.13206v1 [astro-ph.EP] for this version)
Submission history
From: Amirhossein Bagheri
[v1] Mon, 27 Sep 2021 17:28:29 UTC (5,841 KB)

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