Interior Structures of Enceladus and Titan with Respect to Oceanic Equations of State
Abstract
We consider the radial structural properties of the icy ocean moons Enceladus and Titan, with particular consideration for the properties of the oceans. Many large icy moons, including the Jovian moons Europa, Ganymede, and Callisto as well as Saturn's Enceladus and Titan, may contain liquid oceans below their surface. For reasons of simplicity and data insufficiency, most studies of the interior properties of these worlds do not fully account for the thermodynamic properties of the materials in those oceans, including their interactions with ices and minerals in their vicinity. The approach of the publicly available PlanetProfile software (Vance et al. 2018) is to compute thermal and compositional properties of icy world oceans, using recently available thermodynamics for ices, aqueous oceans, rocky layer, and, if present, any iron cores. Boundary conditions of the temperatures at the surface and at the ice-ocean interface below the icy exterior are used to propagate density and temperature profiles radially inward. Ice bottom temperature Tb is thus a proxy for ice thickness. As an example, for an ocean composition of 10 wt% MgSO4 at Enceladus, we investigate ice thicknesses between 19 km and 27 km (Beuthe 2016), corresponding to Tb =273.032 K and 272.954 K, respectively. Currently, PlanetProfile also provides consistency with bulk density and gravitational moment of inertia. Here, we consider the changes to internal structure from a reduced moment of inertia for Titan, accounting for the requirement at Titan for a high ocean density imposed by the large value of the gravitational potential Love number k2 (Mitri et al. 2014). We compute updated tidal dissipation properties (k2, h2, Q) assuming an Andrade rheology for solids. We also discuss recent revisions to the equations of state used by PlanetProfile, employing the local basis functions approach (Brown 2018) to incorporate recently acquired laboratory measurements of thermodynamics in ices aqueous solutions.
A part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2018. All rights reserved.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P21E3389V
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 4599 General or miscellaneous;
- OCEANOGRAPHY: PHYSICALDE: 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 6299 General or miscellaneous;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS