Gravitational constraints on the internal structure of Ganymede (original) (raw)
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- Published: 12 December 1996
Nature volume 384, pages 541–543 (1996)Cite this article
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Abstract
BEFORE the arrival of the Galileo spacecraft in the jovian system, there was little information on the interior structure of Jupiter's largest moon, Ganymede. Its mean density (1,940 kg m−3), determined by the Pioneer and Voyager spacecraft1–3, implies a composition that is roughly 60% rock and 40% ice, which could be uniformly mixed or differentiated into a rocky core and icy mantle4. Here we report measurements by the Galileo spacecraft of Ganymede's overall density and the spherical harmonics, _J_2 and _C_22, of its gravitational field. These data show clearly that Ganymede has differentiated into a core and mantle. Combined with the recent discovery of an intrinsic magnetic field5,6, our gravity results suggest that Ganymede has a metallic core of radius 400–1,300 km surrounded by a silicate mantle, which is in turn enclosed by an ice shell ∼800 km thick. Depending on whether the core is pure iron or an alloy of iron and iron sulphide, it could account for as little as 1.4% or as much as one-third of the total mass. If the ice were stripped away, Ganymede could look much like Io7 in terms of its size and internal mass distribution.
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Authors and Affiliations
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109–8099, USA
J. D. Anderson, E. L. Lau & W. L. Sjogren - Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, 90095-1567, USA
G. Schubert & W. B. Moore
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- J. D. Anderson
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Anderson, J., Lau, E., Sjogren, W. et al. Gravitational constraints on the internal structure of Ganymede.Nature 384, 541–543 (1996). https://doi.org/10.1038/384541a0
- Received: 08 October 1996
- Accepted: 12 November 1996
- Issue Date: 12 December 1996
- DOI: https://doi.org/10.1038/384541a0
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