Mass anomalies on Ganymede

Palguta, J.; Anderson, J. D.; Schubert, G.; Moore, W. B.

doi:10.1016/j.icarus.2005.08.020

Cited by 37 publications

(32 citation statements)

References 14 publications

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“…While gravitational and topographic datasets can each be used independently to make inferences about the interior structure of a planet, such results are often based upon hypotheses that are not easily testable or models that are highly underconstrained. Thus, although regional topographic models have been constructed for some moons and asteroids (such as Phobos (Wählisch et al, 2010), 433 Eros (Gaskell et al, 2008;Zuber et al, 2000a), Itokawa (Abe et al, 2006;Gaskell et al, 2008), Vesta ( Jaumann et al, 2012), Ganymede (Giese et al, 1998), Europa (Nimmo et al, 2003a,b;Nimmo et al, 2007), Iapetus (Giese et al, 2008), Mimas (Dermott and Thomas, 1988), Enceladus , Tethys , Dione , Rhea , and many of the irregularly shaped satellites of Saturn (Thomas, 2010)) and the longest wavelength gravitational fields and topography have been constrained for others (such as Io (Anderson et al, 2001a;Thomas et al, 1998), Europa (Anderson et al, 1998), Ganymede (Anderson et al, 1996b;Palguta et al, 2006), Callisto (Anderson et al, 2001b), Rhea (Anderson and Schubert, 2010), Titan (Iess et al, 2010;Lorenz et al, 2013), and Vesta (Konopliv et al, 2013a)), this chapter will focus on those planetary bodies for which the gravity and topography are both characterized to high resolution, namely, Earth, Venus, Mars, Mercury, and the Moon.…”

Section: Introductionmentioning

confidence: 99%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

129

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Section: Introductionmentioning

confidence: 99%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

129

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“…Flybys of Ganymede, Jupiter's largest moon, by NASA's Galileo spacecraft provided the most detailed view to date of its internal structure and dynamics [e.g., Anderson et al , 1996; Kivelson et al , 1996; Schubert et al , 1996; Palguta et al , 2006]. Ganymede is the most centrally concentrated, largely solid body known in the solar system as indicated by the nondimensional polar moment of inertia ( C / MR 2 ) of 0.3115 [ Schubert et al , 2004].…”

Section: Introductionmentioning

confidence: 99%

Sulfur's impact on core evolution and magnetic field generation on Ganymede

2006

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[1] Analysis of the melting relationships of potential core forming materials in Ganymede indicate that fluid motions, a requirement for a dynamo origin for the satellite's magnetic field, may be driven, in part, either by iron (Fe) ''snow'' forming below the coremantle boundary or solid iron sulfide (FeS) floating upward from the deep core. Eutectic melting temperatures and eutectic sulfur contents in the binary Fe-FeS system decrease with increasing pressure within the interval of core pressures on Ganymede (<14 GPa).Comparison of melting temperatures to adiabatic temperature gradients in the core suggests that solid iron is thermodynamically stable at shallow levels for bulk core compositions more iron-rich than eutectic (i.e., <21 wt % S). Calculations based on highpressure solid-liquid phase relationships in the Fe-FeS system indicate that iron snow or floatation of solid iron sulfide, depending on whether the core composition is more or less iron-rich than eutectic, is an inevitable consequence of cooling Ganymede's core. These results are robust over a wide range of plausible three-layer internal structures and thermal evolution scenarios. For precipitation regimes that include Fe-snow, we present scaling arguments that give typical Rossby and magnetic Reynolds numbers consistent with dynamo action occurring in Ganymede's core. Furthermore, by applying recently derived scaling relationships relating magnetic field strength to buoyancy flux, we obtain estimates of surface magnetic field strength comparable with observed values.

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“…However, as a consequence of the well known degeneracy of gravity, even a complete knowledge of all harmonics coefficients would not be sufficient to provide the local density. The density distribution can be recovered only if the observational data are combined with models of the interior structure, by means of inversion techniques (see, for example, Palguta et al 2006). Unfortunately the paucity of observational data severely limits the knowledge of the harmonic coefficients of icy satellites.…”

Section: The Mathematical Description Of Satellite Gravity Shape Andmentioning

confidence: 99%

“…The two Ganymede gravity flybys occurred at altitudes of 835 and 260 km. The latter was low enough to provide for a clear detection of gravity disturbances (up to 1.5 mgal at the flyby altitude) produced by mass anomalies beneath the surface (Anderson et al 2004;Palguta et al 2006). The large signature in the Doppler data could be removed by introducing four mass anomalies (two positive and two negative) in the orbital solution, in addition to the usual quadrupole coefficients.…”

Section: Gravity Fields Of Jupiter and Saturn Satellitesmentioning

confidence: 99%

Environments in the Outer Solar System

et al. 2010

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The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating objects on their own. Their intrinsic magnetic fields form magnetic environments (so called magnetospheres) in which charged and neutral particles and dust are produced, lost or being transported through the system. These magnetic environments of the gas giants can be envisaged as huge plasma laboratories in space in which electromagnetic waves, current systems, particle transport mechanisms, acceleration processes and other phenomena act and interact with the large number of moons in orbit around those massive planets. In general it is necessary to describe and study the global environments (magnetospheres) of the gas giants, its global configuration with its large-scale transport processes; and, in combination, to study the local environments of the moons as well, e.g. the interaction processes between the magnetospheric plasma and the exosphere/atmosphere/magnetosphere of the moon acting on time scales of seconds to days. These local exchange processes include also the gravity, shape, rotation, astrometric observations and orbital parameters of the icy moons in those huge systems. It is the purpose of this chapter of the book to describe the variety of the magnetic environments of the outer planets in a broad overview, globally and locally, and to show that those exchange processes can dramatically influence the surfaces and exospheres/atmospheres of the moons and they can also be used as a tool to study the overall physics of systems as a whole

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Mass anomalies on Ganymede

Cited by 37 publications

References 14 publications

Gravity and Topography of the Terrestrial Planets

Gravity and Topography of the Terrestrial Planets

Sulfur's impact on core evolution and magnetic field generation on Ganymede

Environments in the Outer Solar System

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