Abstract
Before the arrival of the Galileo spacecraft at Jupiter, models for the interior structure of the four galilean satellites—Io, Europa, Ganymede and Callisto—ranged from uniform mixtures of rock and ice (that is, undifferentiated objects) or rocky cores surrounded by a mantle of water ice1. Now it appears that lo has a large metallic core2 and that Ganymede is strongly differentiated, most probably into a three-layer structure consisting of a metallic core, a silicate mantle and a deep outer layer of ice3. Direct information on the interior structure of Callisto determined from previous spacecraft fly-bys4–6 was essentially limited to an estimate of the mean density being intermediate between pure ice and pure rock. Here we report measurements of Callisto's gravitational field which reveal that, in contrast to Io and Ganymede, this galilean satellite is most probably a homogeneous object consisting of a solar mixture of 40% compressed ice and 60% rock (including iron and iron sulphide). Callisto's undifferentiated state is consistent with the apparent lack of an intrinsic magnetic field7, and indicates that the outermost galilean satellite has not experienced a heating phase sufficiently high to separate its rock and metal components from the lighter ices.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Schubert, G., Spohn, T. & Reynolds, R. T. in Satellites (eds Burns, J. A. & Matthews, M. S.) 629–688 (Univ. Arizona Press, Tucson, 1986).
Anderson, J. D., Sjogren, W. L. & Schubert, G. Science 272, 709–712 (1996).
Anderson, J. D., Lau, E. L., Sjogren, W. L., Schubert, G. & Moore, W. B. Nature 384, 541–543 (1996).
Null, G. W., Anderson, J. D. & Wong, S. K. Science 12, 476–477 (1975).
Null, G. W. Astron. J. 81, 1153–1161 (1976).
Campbell, J. K. & Synnott, S. P. Astron. J. 90, 364–372 (1985).
Khurana, K. K., Kivelson, M. G., Russell, C. T., Walker, R. J. & Southwood, D. J. Absence of an internal magnetic field at Callisto. Nature 387, 262–264 (1997).
Moyer, T. D. Orbit Determination Program (Tech. Rep. No. TR32–1527, Jet Propulsion Lab., Pasadena, 1971).
Anderson, J. D. in Experimental Gravitation (ed. Bertotti, B.) 163–199 (Academic, New York, 1974).
Tapley, B. D. in Recent Advances in Dynamical Astronomy (eds Tapley, B. D. & Szebehely, V.) 396–425 (Reidel, Dordrecht, 1973).
Kaula, W. M. Theory of Satellite Geodesy (Blaisdell, Waltham, MA, 1966).
Hubbard, W. B. & Anderson, J. D. Icarus 33, 336–341 (1978).
Kaula, W. M. An Introduction to Planetary Physics: The Terrestrial Planets (Wiley, New York, 1968).
Dermott, S. F. Icarus 37, 310–321 (1979).
Zharkov, V. N., Leontjev, V. V. & Kozenko, A. V. Icarus 61, 92–100 (1985).
Jeffreys, H. The Earth (Cambridge Univ. Press, 1962).
Schubert, G., Limonadi, D., Anderson, J. D., Campbell, J. K. & Giampieri, G. Icarus 111, 433–440 (1994).
Schubert, G., Zhang, K., Kivelson, M. G. & Anderson, J. D. Nature 384, 544–545 (1996).
Malhotra, R. Icarus 94, 399–412 (1991).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Anderson, J., Lau, E., Sjogren, W. et al. Gravitational evidence for an undifferentiated Callisto. Nature 387, 264–266 (1997). https://doi.org/10.1038/387264a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/387264a0
This article is cited by
-
Environments in the Outer Solar System
Space Science Reviews (2010)
-
Models of the Internal Structure of Callisto
Solar System Research (2005)
-
Cassini Radio Science
Space Science Reviews (2004)
-
A Comprehensive Orbit Reconstruction for the Galileo Prime Mission in the J2000 System
The Journal of the Astronautical Sciences (2000)
-
Galileo at Jupiter — meetings with remarkable moons
Nature (1997)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.