Saturn's icy satellites: Thermal and structural models

Ellsworth, K.; Schubert, G.

doi:10.1016/0019-1035(83)90242-7

Cited by 160 publications

(92 citation statements)

References 29 publications

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“…Both these energies are possibly larger for mixed ices, and should partly compensate A82, page 8 of 24 Stewart (1960) ; (d) Giauque & Blue (1936) ; (e) Prialnik et al (2004) ; ( f ) Giauque & Stout (1936) ; (g) Handa & Klug (1988) ; (h) Clayton & Giauque (1932) ; (i) Giauque & Egan (1937) ; ( j) Ellsworth & schubert (1983) ; (k) Grun et al (1993) and Huebner et al (2006) ; (l) Klinger (1980) ; (m) data fit of Stachowiak et al (1998) ; (n) data fit of Koloskova et al (1974) ; (o) data fit of Manzhelii & Krupskii (1968) ; (p) Ghormley (1968) ; (q) expressions given in Fray & Schmitt (2009) . in the sum, but without experimental knowledge of their values and dependences they cannot be taken into account in our model.…”

Section: Thermodynamic Parametersmentioning

confidence: 99%

“…The heat conductivity of amorphous ice containing trapped molecules is assumed to be the same as that of pure amorphous ice. The heat conductivity of dust grains is from Ellsworth & schubert (1983). For a dust mantle at the surface of the nucleus, laboratory experiments (see Grün et al 1993;and Huebner et al 2006 for a review), showed that the thermal conductivity of dust layers composed by silicate particles is very low (about 10 −2 to 10 −3 W m −1 K −1 ).…”

Section: Thermodynamic Parametersmentioning

confidence: 99%

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A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Marboeuf

Schmitt

Petit

et al. 2012

A&A

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Context. Current theories, models of cometary nuclei and of ice formation in the protoplanetary disk, and laboratory studies suggest that cometary materials could be formed of pure crystalline water ice, amorphous water ice, clathrate hydrate, or a mixture of these structures of water ice. However, current models of cometary nuclei consider only two forms of ice during the thermodynamic evolution of comets: amorphous and crystalline water ices. Aims. In this work, we have developed a model of cometary nucleus that takes into account all water ice structures and phase changes in order to predict the outgassing profile of volatile molecules that could be measured by the Rosetta mission and can be used to constrain the structural type of ice existing in the interior of the Comet 67P/Churyumov-Gerasimenko, the target comet of the Rosetta mission, and, hopefully, its initial composition. Methods. We added the physic of formation/dissociation of clathrate hydrates in addition to others physical processes that are taken into account in models without clathrate hydrates. All thermal changes, as well as the release and trapping of gas with water phase changes are taken into account. Results. This model describes heat transmission, latent heat exchanges, all water ices structures and transitions (amorphous-to-pure crystalline, amorphous-to-clathrate hydrates and pure crystalline-to-clathrate hydrates and vise versa), sublimation/recondensation of volatile molecules in the nucleus, gas diffusion, gas released and trapped by crystallization and clathrate formation/dissociation processes, as well as gas and dust release and mantle formation at the surface. Applying this model to the comet 67P/ChuryumovGerasimenko, results show different outgassing profiles of volatiles molecules from the nucleus depending on the water ice structure, the distribution of volatile molecules between the "trapped" and "condensed" states in the nucleus and the thermal inertia of its porous matrix. Conclusions. Given these results, we pretend that this model is able to constrain the water ice structure and chemical composition in comets from outgassing profiles of volatile molecules, and especially those of the target comet of the Rosetta mission.

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Section: Thermodynamic Parametersmentioning

confidence: 99%

Section: Thermodynamic Parametersmentioning

confidence: 99%

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Marboeuf

Schmitt

Petit

et al. 2012

A&A

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“…Previous attempts to model the physical structure of Rhea have been carried out by Consolmagno & Lewis (1978), Lupo & Lewis (1979), Ellsworth & Schubert (1983), and Consolmagno (1985). All these authors have assumed a bulk chemical composition of rock and water ice in the mass-percent proportions 60:40.…”

Section: Previous Modelling Of Rheamentioning

confidence: 99%

“…The maximum melting radius is attained after about 500 Myr. Ellsworth & Schubert (1983) were the first to explicitly model convective heat transfer in icy satellites. According to these authors, the Rayleigh number quickly rises above the critical value of approximately 1100 required for the onset of convection in a Rhea-sized radiogenically heated icy satellite.…”

Section: Examining the Possibility Of Melting Of Icementioning

confidence: 99%

Saturn's Icy Moon Rhea: A Prediction for its Bulk Chemical Composition and Physical Structure at the Time of the Cassini Spacecraft First Flyby

Prentice¹

2006

Publ. – Astron. Soc. Aust

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I report a model for the formation of Saturn's family of mid-sized icy moons to coincide with the first flypast of Rhea by the Cassini spacecraft on 2005 November 26. It is proposed that the moons had condensed from a concentric family of orbiting gas rings that were shed some 4.6610 9 yr ago by the proto-Saturnian (hereafter p-Sat) cloud. The p-Sat cloud is made up of gas and residual grains of the gas ring that was shed by the proto-Solar cloud (hereafter PSC) at Saturn's orbit. The bulk of the condensate within this proto-Solar ring accumulates to form Saturn's central core of mass~10-20 M È (M È = Earth mass). The process of formation of Saturn's solid core thus provides an opportunity for the p-Sat cloud to become depleted in rock and water ice relative to the usual solar abundances of these materials. Nitrogen, which exists as uncondensing N 2 in the PSC and as NH 3 in the p-Sat cloud, retains its solar abundance relative to H 2 . If the depletion factor of solids relative to gas is z dep = 0.25, as suggested by the low mass of Rhea relative to solar abundance expectations, the mass-percent ratio of NH 3 to H 2 O in the dense p-Sat cloud is 36:64. Numerical and structural models for Rhea are constructed on the basis of a 'cosmogonic' bulk chemical composition of hydrated rock (mass fraction 0.385), H 2 O ice (0.395), and NH 3 ice (0.220). It is difficult to construct a chemically differentiated model of Rhea whose mean density matches the observed value r Rhea = 1.23 ± 0.02 g cm -3 for reasonable bounds of the controlling parameters. Chemically homogeneous models can, however, be constrained to match the observed Rhea density provided that the mass fraction of NH 3 is permitted to exceed the cosmogonic value by a factor z NH 3 = 1.20-1.35. A large proportion of NH 3 in the ice mass inhibits the formation of the dense crystalline phase II of H 2 O ice at high pressure. This may explain the lack of compressional features on the surface of the satellite that are expected as a result of ice II formation in the cooling core. The favoured model of Rhea is chemically uniform and has mass proportions of rock (0.369), H 2 O ice (0.378), and NH 3 ice (0.253). The enhancement factor of NH 3 lies within the measured uncertainties of the solar abundance of nitrogen. The satellite is very cold and nearly isodense. The predicted axial moment-of-inertia coefficient is [C/MR 2 ] Rhea = 0.399 ± 0.004.

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“…The solid curve in Figure 4 shows the temperature profile in an outer ice layer on Enceladus, calculated by means of equation (1) assuming a surface temperature of 80 K (Ellsworth and Schubert, 1983) and a surface heat flow of 5 mW m )2 (it is necessary remind that this heat flow value is an upper limit). Ice melting temperature (assumed as 273 K), is reached at 140 km depth.…”

Section: The Effect Of the Spherical Geometry On The Temperature-deptmentioning

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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Saturn's icy satellites: Thermal and structural models

Cited by 160 publications

References 29 publications

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Saturn's Icy Moon Rhea: A Prediction for its Bulk Chemical Composition and Physical Structure at the Time of the Cassini Spacecraft First Flyby

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

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