Tidal heating in an internal ocean model of Europa

Ross, M. N.; Schubert, G.

doi:10.1038/325133a0

Cited by 94 publications

(73 citation statements)

References 17 publications

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“…Vertical heat flows of at least ϳ100 -200 mW m Ϫ2 are needed to put the brittleductile transition at a depth Յ2 km (McKinnon, 2000;Pappalardo et al, 1999b;Ruiz andTejero, 1999, 2000). These heat flows are clearly higher than the theoretical values of Յ50 mW m Ϫ2 calculated by classical tidal heating models (Cassen et al, 1982;Ojakangas and Stevenson, 1989;Ross and Schubert, 1987;Squyres et al, 1983) . The explanation for these high heat flows could lie in the tidal heating either of a warm ice convective layer (McKinnon and Shock, 2001;Ruiz and Tejero, 2000) or of the rock/ metal core (McKinnon and Shock, 2001).…”

Section: Introductionmentioning

confidence: 51%

“…Later on, Squyres et al (1983) calculated that an icy shell in Europa would be stable against convection if its thickness did not exceed ϳ30 km. Based on this, it was proposed that tidal heating could perhaps allow the stable existence of a conductive shell floating over an internal liquid-water ocean (Ojakangas and Stevenson, 1989;Ross and Schubert, 1987;Squyres et al, 1983).…”

Section: Shell Thickness and Heat Flow In The Onset Of Convectionmentioning

confidence: 99%

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Heat flow, lenticulae spacing, and possibility of convection in the ice shell of europa

Ruíz

Tejero

2003

Icarus

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Two opposing models to explain the geological features observed on Europa's surface have been proposed. The thin-shell model states that the ice shell is only a few kilometers thick, transfers heat by conduction only, and can become locally thinner until it exposes an underlying ocean on the satellite's surface. According to the thick-shell model, the ice shell may be several tens of kilometers thick and have a lower convective layer, above which there is a cold stagnant lid that dissipates heat by conduction. Whichever the case, from magnetic data there is strong support for the presence of a layer of salty liquid water under the ice. The present study was performed to examine whether the possibility of convection is theoretically consistent with surface heat flows of ϳ100 -200 mW m Ϫ2 , deduced from a thin brittle lithosphere, and with the typical spacing of 15-23 km proposed for the features usually known as lenticulae. It was obtained that under Europa's ice shell conditions convection could occur and also account for high heat flows due to tidal heating of the convective (nearly isothermal) interior, but only if the dominant water ice rheology is superplastic flow (with activation energy of 49 kJ mol Ϫ1 ; this is the rheology thought dominant in the warm interior of the ice shell). In this case the ice shell would be ϳ15-50 km thick. Furthermore, in this scenario explaining the origin of the lenticulae related to convective processes requires ice grain size close to 1 mm and ice thickness around 15-20 km.

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Section: Introductionmentioning

confidence: 51%

Section: Shell Thickness and Heat Flow In The Onset Of Convectionmentioning

confidence: 99%

Heat flow, lenticulae spacing, and possibility of convection in the ice shell of europa

Ruíz

Tejero

2003

Icarus

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“…For a model of Europa that includes dynamic decoupling between icy shell and rocky core by an ocean, the minimum contribution to the heat flow by tidal heating in the core would be~12-16 mW m )2 (Squyres et al, 1983;Ross and Schubert, 1987). Thus, heat flow reaching to the icy shell base from the rock and metal core would be at least~20 mW m )2 (which is equivalent to a shell at most~30 km thick).…”

Section: Results and Conclusionmentioning

confidence: 99%

“…This allows us to relate the feasibility analysis for convection initiation to the thermal state of Europa. A higher effective surface temperature (caused, for example, by an insulating regolith layer (e.g., Shoemaker et al, 1982;Ross and Schubert, 1987), or by a solid-state greenhouse in the uppermost superficial ice layer (e.g., Matson and Brown, 1989)) reduces the ice shell thickness required for the onset of convection. However, the critical heat flow at the onset of convection is almost independent of the surface temperature (Ruiz and Tejero, 2003).…”

Section: Results and Conclusionmentioning

confidence: 99%

Possibility of Convection for Diffusion (Newtonian) Viscosity in the Ice Shell of Europa?

2003

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Abstract. Recent investigations into convection in Europa's ice shell have been based on nonNewtonian (stress-dependent) or Newtonian (stress-independent) viscosity for water ice. However, despite the wide use of Newtonian convection, experimentally observed water ice flow is non-Newtonian, and analysis of stability against convection of the ice shell using updated flow laws has been only performed for non-Newtonian rheologies. Here we use the flow law proposed for diffusion creep to analyze the possibility of the onset of convection for Newtonian viscosity in relation to the thermal state of Europa. Our findings indicate that for diffusion creep convection might have started, but that significantly lower heat flows (and equivalently higher shell thicknesses) and/or grain sizes are required than for superplastic flow, which is the most probable flow mechanism if the ice shell is convective.

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“…These effects, frequently cited by the icy Galilean satellites (e.g., Shoemaker et al, 1982;Squyres et al, 1983;Ross and Schubert, 1987), could contribute to retain internal heat, favoring the existence of an internal ocean. Similarly, the possibility of a surface layer rich in low thermal conductivity ices raising the effective surface temperature and contributing to a hotter interior on Triton has been mentioned by McKinnon et al (1995).…”

Section: Insulating Layers On the Surfacementioning

confidence: 99%

Seas under ice: Stability of liquid-water oceans within icy worlds

Ruíz

Fairén

2005

Earth Moon Planet

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Abstract. The present-day existence of internal oceans under the outer ice shell of several icy satellites of the Solar System has been recently proposed. The presence of antifreeze substances decreasing ice's melting point (and tidal heating in Europa's case) has been generally believed to allow the stability of such oceans; limited cooling of the water (ice plus liquid) layer, due to stability against convection or to stagnant lid convection in the icy shell, have been also considered. Here we propose that even pure liquidwater oceans could survive today within several icy worlds, and we consider some factors affecting thermal modeling in these bodies. So, the existence of such oceans would be a natural consequence of the physical properties of water ice, independently from the addition of antifreeze substances or any other special conditions. The inclusion of these substances would contribute to expand the conditions for water to stay liquid and to increase ocean's volume.

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Tidal heating in an internal ocean model of Europa

Cited by 94 publications

References 17 publications

Heat flow, lenticulae spacing, and possibility of convection in the ice shell of europa

Heat flow, lenticulae spacing, and possibility of convection in the ice shell of europa

Possibility of Convection for Diffusion (Newtonian) Viscosity in the Ice Shell of Europa?

Seas under ice: Stability of liquid-water oceans within icy worlds

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