Interiors and Evolution of Icy Satellites

Hußmann, H.

doi:10.1016/b978-044452748-6.00168-1

Cited by 14 publications

(14 citation statements)

References 167 publications

(236 reference statements)

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“…Nevertheless, our model may overestimate the effect of a lid since we assume that the shell has a uniform viscosity structure for simplicity. The viscosity of an icy shell of actual satellites, however, would vary largely with depth [e.g., Hussmann et al, 2007]; the viscosity of the near-surface layer would be very high while that of the base of the shell would be much lower. Consequently, the thickness of a stiff lid may be much thinner than that of the icy shell.…”

Section: Discussionmentioning

confidence: 99%

“…Most of the satellites of Jupiter and Saturn are covered by an icy shell because of the low surface temperature. Based on internal thermal and structural modeling, large icy satellites, such as Europa and Titan, are expected to possess an internal ocean underneath an icy shell [e.g., Hussmann et al, 2007]. This expectation is supported from observational data by the Galileo and Cassini spacecraft and by the Hubble Space Telescope [e.g., Kivelson et al, 2000Kivelson et al, , 2002Iess et al, 2012;Saur et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

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Tidal resonance in icy satellites with subsurface oceans

2015

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Tidal dissipation is a major heat source for the icy satellites of the giant planets. Several icy satellites likely possess a subsurface ocean underneath an ice shell. Previous studies of tidal dissipation on icy satellites, however, have either assumed a static ocean or ignored the effect of the ice lid on subsurface ocean dynamics. In this study, we examine inertial effects on tidal deformation of satellites with a dynamic ocean overlain by an ice lid based on viscoelasto-gravitational theory. Although ocean dynamics is treated in a simplified fashion, we find a resonant configuration when the phase velocity of ocean gravity waves is similar to that of the tidal bulge. This condition is achieved when a subsurface ocean is thin (<1 km). The enhanced deformation (increased h 2 and k 2 Love numbers) near the resonant configuration would lead to enhanced tidal heating in the solid lid. A static ocean formulation gives an accurate result only if the ocean thickness is much larger than the resonant thickness. The resonant configuration strongly depends on the properties of the shell, demonstrating the importance of the presence of a shell on tidal dissipation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tidal resonance in icy satellites with subsurface oceans

2015

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“…The cooling of icy satellites is controlled by the heat transfer through their outer ice layer [Hussmann et al, 2007]. The physical (thickness and thermal conductivity) and rheological (viscosity) properties of this layer allow thermal convection to operate within it and thus to enhance heat transport from the satellite's interior toward its surface.…”

Section: Introductionmentioning

confidence: 99%

Stagnant lid convection in bottom-heated thin 3-D spherical shells: Influence of curvature and implications for dwarf planets and icy moons

Yao¹,

Deschamps

Lowman

et al. 2014

J. Geophys. Res. Planets

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(2014), Stagnant lid convection in bottom-heated thin 3-D spherical shells: Influence of curvature and implications for dwarf planets and icy moons, J. Geophys. Res. Planets, 119, 1895-1913, doi:10.1002 Abstract Because the viscosity of ice is strongly temperature dependent, convection in the ice layers of icy moons and dwarf planets likely operates in the stagnant lid regime, in which a rigid lid forms at the top of the fluid and reduces the heat transfer. A detailed modeling of the thermal history and radial structure of icy moons and dwarf planets thus requires an accurate description of stagnant lid convection. We performed numerical experiments of stagnant lid convection in 3-D spherical geometries for various ice shell curvatures f (measured as the ratio between the inner and outer radii), effective Rayleigh number Ra m , and viscosity contrast Δ . From our results, we derived scaling laws for the average temperature of the well-mixed interior, m , and the heat flux transported through the shell. The nondimensional temperature difference across the bottom thermal boundary layer is well described by (1 − m ) = 1.23 f 1.5 , where is a parameter that controls the magnitude of the viscosity contrast. The nondimensional heat flux at the bottom of the shell, F bot , scales as F bot = 1.46Ra 0.27 m 1.21 f 1.78 . Our models also show that the development of the stagnant lid regime depends on f . For given values of Ra m and Δ , the stagnant lid is less developed as the shell's curvature increases (i.e., as f decreases), leading to improved heat transfer. Therefore, as the outer ice shells of icy moons and dwarf planets grow, the effects of a stagnant lid are less pronounced.

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“…Additionally, self-sustained and/or induced magnetic fields, surface geology and composition, and the volatile inventory of a planet or satellite provide indirect information about the constitution of planetary and satellite interiors. Tectonic manifestations of endogenic activity preserved in the long-term surface record are particularly useful to infer the mode of internal heat transport (e.g., Schubert et al 1986, Hussmann et al 2007.…”

mentioning

confidence: 99%

“…Superimposed are time-variable contributions which are induced by radial and librational tides along slightly eccentric orbits of a number of satellites. From the analysis of Doppler range and range rate observations acquired at around closest approach, the axial moments of inertia of only a few satellites have been inferred from gravitational perturbations on spacecraft trajectories by using the RadauDarwin relation (e.g., Hussmann et al 2007). However, the moment-of-inertia values derived in this way are almost entirely based on the assumption that the satellites are in Icy Satellite Interiors 115 hydrostatic equilibrium and the ratio J 2 /C 2,2 taken constant at 10/3.…”

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confidence: 99%

Interior Models of Icy Satellites and Prospects of Investigation

Sohl

2009

Proc. IAU

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Abstract. The state of knowledge about the structure and composition of icy satellite interiors has been significantly extended by combining direct measurements from spacecraft, laboratory experiments, and theoretical modeling. Interior models of icy bodies will certainly benefit from future missions to the outer solar system, providing new and improved constraints on the surface chemistry, bulk composition and degree of internal differentiation, possible heterogeneities in radial mass distribution, the presence and extent of liquid reservoirs, and the amount of tidal heating for each target body. Here we summarize geophysical constraints on the interior structure and composition of selected Jovian and Saturnian icy satellites and investigate conditions under which potentially habitable liquid water reservoirs could be maintained. Future geophysical exploration which includes gravitational and magnetic field sounding from low-altitude orbit and close flyby, combined with altimetry data and in-situ monitoring of tidally-induced surface distortion and time-variable magnetic fields, would impose important constraints on the interiors of outer planet satellites.

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Interiors and Evolution of Icy Satellites

Cited by 14 publications

References 167 publications

Tidal resonance in icy satellites with subsurface oceans

Tidal resonance in icy satellites with subsurface oceans

Stagnant lid convection in bottom-heated thin 3-D spherical shells: Influence of curvature and implications for dwarf planets and icy moons

Interior Models of Icy Satellites and Prospects of Investigation

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