Europa's differentiated internal structure: Inferences from two Galileo encounters

Science

Volumn 276, Issue 5316, 1997, Pages 1236-1239

  Anderson, J D ^a   Lau, E L ^a   Sjogren, W L ^a   Schubert, G ^b   Moore, W B ^b  

^a CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ASTRONOMY; GRAVITY; MAGNETIC FIELD; PRIORITY JOURNAL; SPACE FLIGHT;

FLIGHT EXPERIMENT; GALILEO PROJECT; LONG DURATION; UNMANNED;

EXTRATERRESTRIAL ENVIRONMENT; ICE; JUPITER;

GALILEO MISSION; GRAVITATIONAL FIELD;

EUROPA;

EID: 0030619671     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.276.5316.1236     Document Type: Article

References (22)

1. For results from the Pioneer 10 and 11 Mission, see G. W. Null, J. D. Anderson, and S. K. Wong [Science 188, 476 (1975)] and G. W. Null [Astron. J. 81, 1153 (1976)]. For results from a combination of radio Doppler data from the Pioneer 10 and 11 missions and from the Voyager 1 and 2 missions, see J. K. Campbell and S. P. Synnott [Astron. J. 90, 364 (1985)].
2. For results from the Pioneer 10 and 11 Mission, see G. W. Null, J. D. Anderson, and S. K. Wong [Science 188, 476 (1975)] and G. W. Null [Astron. J. 81, 1153 (1976)]. For results from a combination of radio Doppler data from the Pioneer 10 and 11 missions and from the Voyager 1 and 2 missions, see J. K. Campbell and S. P. Synnott [Astron. J. 90, 364 (1985)].
3. For results from the Pioneer 10 and 11 Mission, see G. W. Null, J. D. Anderson, and S. K. Wong [Science 188, 476 (1975)] and G. W. Null [Astron. J. 81, 1153 (1976)]. For results from a combination of radio Doppler data from the Pioneer 10 and 11 missions and from the Voyager 1 and 2 missions, see J. K. Campbell and S. P. Synnott [Astron. J. 90, 364 (1985)].
4. G. Schubert, T. Spohn, R. T. Reynolds, in Satellites, J. A. Burns and M. S. Matthews, Eds. (Univ. of Arizona Press, Tucson, 1986), pp. 629-688.
5. J. D. Anderson, E. L. Lau, W. L. Sjogren, G. Schubert, W. B. Moore, Nature 384, 541 (1996).
6. J. D. Anderson, W. L. Sjogren, G. Schubert, Science 272, 709 (1996).
7. J. D. Anderson, E. L. Lau, W. L. Sjogren, G. Schubert, W. B. Moore, Nature, in press.
8. See, for example, T. D. Moyer, Tech. Rep. No. TR 32-1527 (Jet Propulsion Laboratory, Pasadena, CA, 1971); B. D. Tapley, in Recent Advances in Dynamical Astronomy, B. D. Tapley and V. Szebehely, Eds. (Reidel, Dordrecht, Netherlands, and Boston, MA, 1973), pp. 396-425; J. D. Anderson, in Experimental Gravitation, B. Bertotti, Ed. (Academic Press, New York, 1974), pp. 163-199.
9. See, for example, T. D. Moyer, Tech. Rep. No. TR 32-1527 (Jet Propulsion Laboratory, Pasadena, CA, 1971); B. D. Tapley, in Recent Advances in Dynamical Astronomy, B. D. Tapley and V. Szebehely, Eds. (Reidel, Dordrecht, Netherlands, and Boston, MA, 1973), pp. 396-425; J. D. Anderson, in Experimental Gravitation, B. Bertotti, Ed. (Academic Press, New York, 1974), pp. 163-199.
10. See, for example, T. D. Moyer, Tech. Rep. No. TR 32-1527 (Jet Propulsion Laboratory, Pasadena, CA, 1971); B. D. Tapley, in Recent Advances in Dynamical Astronomy, B. D. Tapley and V. Szebehely, Eds. (Reidel, Dordrecht, Netherlands, and Boston, MA, 1973), pp. 396-425; J. D. Anderson, in Experimental Gravitation, B. Bertotti, Ed. (Academic Press, New York, 1974), pp. 163-199.
11. W. M. Kaula, Theory of Satellite Geodesy (Blaisdell, Waltham, MA, 1966).
12. 2 φ cos 2λ] (2) The reference radius for Europa is R = 1560 km.
13. The first encounter with Europa on 19 December 1996 occurred at 06:52:57.7 UTC (spacecraft time) at an altitude of 692 km (above the reference sphere), a latitude φ = -1.68° and a longitude λ= 323.16° (east longitude). The second encounter on 20 February 1997 occurred at 17:06:10.2 UTC at an altitude of 586 km, a latitude φ = -17.01° and a longitude λ = 35.31° (east longitude).
14. -3.
15. -3.
16. For example, W. M. Kaula, An Introduction to Planetary Physics: The Terrestrial Planets (Wiley, New York, 1968); W. B. Hubbard and J. D. Anderson, Icarus 33, 336 (1978); S. F. Dermott, ibid. 37, 310 (1979); V. N. Zharkov, V. V. Leontjev, A. V. Kozenko, ibid. 61, 92 (1985).
17. For example, W. M. Kaula, An Introduction to Planetary Physics: The Terrestrial Planets (Wiley, New York, 1968); W. B. Hubbard and J. D. Anderson, Icarus 33, 336 (1978); S. F. Dermott, ibid. 37, 310 (1979); V. N. Zharkov, V. V. Leontjev, A. V. Kozenko, ibid. 61, 92 (1985).
18. For example, W. M. Kaula, An Introduction to Planetary Physics: The Terrestrial Planets (Wiley, New York, 1968); W. B. Hubbard and J. D. Anderson, Icarus 33, 336 (1978); S. F. Dermott, ibid. 37, 310 (1979); V. N. Zharkov, V. V. Leontjev, A. V. Kozenko, ibid. 61, 92 (1985).
19. For example, W. M. Kaula, An Introduction to Planetary Physics: The Terrestrial Planets (Wiley, New York, 1968); W. B. Hubbard and J. D. Anderson, Icarus 33, 336 (1978); S. F. Dermott, ibid. 37, 310 (1979); V. N. Zharkov, V. V. Leontjev, A. V. Kozenko, ibid. 61, 92 (1985).
20. H. Jeffreys, The Earth (Cambridge Univ. Press, London, 1962).
21. M. G. Kivelson et al., Science 276, 1239 (1997).
22. This experiment was coordinated at JPL by the Radio Science Systems Group under R. G. Herrera and S. Asmar. The radio Doppler data were generated with the support of the Telecommunications and Mission Operations Directorate and the Deep Space Network (DSN). The data analysis depended on the availability of software and personnel of the Galileo Project Navigation Team, W. E. Kirhofer, Team Leader. This work was sponsored by the Galileo Project and was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. G.S. and W.B.M. acknowledge support by grants from NASA through the Galileo Project at JPL and the Planetary Geology and Geophysics Program.