Galileo imaging of atmospheric emissions from Io

Science

Volumn 285, Issue 5429, 1999, Pages 870-874

  Geissler, P E ^a   McEwen, A S ^a   Ip, W ^b   Belton, M J S ^c   Johnson, T V ^d   Smyth, W H ^e   Ingersoll, A P ^f  

^a UNIVERSITY OF ARIZONA   (United States)

^b NATIONAL CENTRAL UNIVERSITY   (Taiwan)

^c NATIONAL OPTICAL ASTRONOMY OBSERVATORY   (United States)

^d CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

^e Atmosph and Environmental Research   (United States)

^f CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ASTRONOMY; IMAGING; PRIORITY JOURNAL; SPACE FLIGHT;

FLIGHT EXPERIMENT; GALILEO PROJECT; LONG DURATION; UNMANNED;

ATMOSPHERE; EXTRATERRESTRIAL ENVIRONMENT; JUPITER; OXYGEN; SODIUM; SULFUR DIOXIDE;

EID: 0033529583     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.285.5429.870     Document Type: Article

References (43)

1. For a comprehensive review, see E. Lellouch, Icarus 124, 1 (1996).
2. Recent observations by the UV spectrometer on Galileo are reported by A. R. Hendrix, C. A. Barth, and C. W. Hord [J. Geophys. Res. 104, 11817 (1999)].
3. R. A. Brown, in Exploration of the Planetary System, Proceedings of the Symposium, Torun, Poland, September 5-8, 1973, A. Woszczyk and C. Iwaniszewska, Eds. (Reidel, Dordrecht, Netherlands, 1974), pp. 527-531; L. M. Trafton, Nature 258, 690 (1975); J. T. Trauger et al., Bull. Am. Astron. Soc. 8, 468 (1976); R. A. Brown, Astrophys. J. 244, 1072 (1981); S. T. Durrance, P. D. Feldman, H. A. Weaver, Astrophys. J. Lett. 267, L125 (1983).
4. R. A. Brown, in Exploration of the Planetary System, Proceedings of the Symposium, Torun, Poland, September 5-8, 1973, A. Woszczyk and C. Iwaniszewska, Eds. (Reidel, Dordrecht, Netherlands, 1974), pp. 527- 531; L. M. Trafton, Nature 258, 690 (1975); J. T. Trauger et al., Bull. Am. Astron. Soc. 8, 468 (1976); R. A. Brown, Astrophys. J. 244, 1072 (1981); S. T. Durrance, P. D. Feldman, H. A. Weaver, Astrophys. J. Lett. 267, L125 (1983).
5. R. A. Brown, in Exploration of the Planetary System, Proceedings of the Symposium, Torun, Poland, September 5-8, 1973, A. Woszczyk and C. Iwaniszewska, Eds. (Reidel, Dordrecht, Netherlands, 1974), pp. 527- 531; L. M. Trafton, Nature 258, 690 (1975); J. T. Trauger et al., Bull. Am. Astron. Soc. 8, 468 (1976); R. A. Brown, Astrophys. J. 244, 1072 (1981); S. T. Durrance, P. D. Feldman, H. A. Weaver, Astrophys. J. Lett. 267, L125 (1983).
6. R. A. Brown, in Exploration of the Planetary System, Proceedings of the Symposium, Torun, Poland, September 5-8, 1973, A. Woszczyk and C. Iwaniszewska, Eds. (Reidel, Dordrecht, Netherlands, 1974), pp. 527- 531; L. M. Trafton, Nature 258, 690 (1975); J. T. Trauger et al., Bull. Am. Astron. Soc. 8, 468 (1976); R. A. Brown, Astrophys. J. 244, 1072 (1981); S. T. Durrance, P. D. Feldman, H. A. Weaver, Astrophys. J. Lett. 267, L125 (1983).
7. R. A. Brown, in Exploration of the Planetary System, Proceedings of the Symposium, Torun, Poland, September 5-8, 1973, A. Woszczyk and C. Iwaniszewska, Eds. (Reidel, Dordrecht, Netherlands, 1974), pp. 527- 531; L. M. Trafton, Nature 258, 690 (1975); J. T. Trauger et al., Bull. Am. Astron. Soc. 8, 468 (1976); R. A. Brown, Astrophys. J. 244, 1072 (1981); S. T. Durrance, P. D. Feldman, H. A. Weaver, Astrophys. J. Lett. 267, L125 (1983).
8. F. L. Roesler et al., Science 283, 353 (1999).
9. A. F. Cook et al., ibid. 211, 1419 (1981).
10. J. M. Ajello, G. K. James, I. Kanik, J. Geophys. Res. 97, 10501 (1992).
11. J. T. Trauger, K. R. Stapelfeldt, G. E. Ballester, J. T. Clarke, WFPC2 Science Team, Bull. Am. Astron. Soc. 29, 1002 (1997).
12. F. Scherb and W. H. Smyth, J. Geophys. Res. 98, 18729 (1993).
13. M. E. Brown et al., in preparation.
14. M. J. S. Belton et al., Science 274, 377 (1996).
15. A. S. McEwen et al., ibid. 281, 87 (1998).
16. Bandpasses listed are the wavelengths over which the system response to white light is at least 1% of the peak value for each filter, to 5-nm precision [H. Breneman and K. Klaasen, Report D-5880 (Jet Propulsion Laboratory, Pasadena, CA, 1993)].
17. The E15 color data were recorded with exposure times (25.6 s) longer than those used In previous attempts and were telemetered with lossless compression. An earlier color sequence from orbit G7 was degraded by accidental multiple exposures.
18. K. P. Klaasen et al., Opt. Eng. 36, 3001 (1997). We have subtracted an empirically determined background component, which was calculated as the average brightness of the region surrounding Io's disk. Brightness estimates are based on the average system response to white light over the entire bandpass of each filter. Hence, line emissions may be underestimated if they occur at wavelengths near the limits of the filters' sensitivity.
19. Total optical power is defined as 4πJA, where A is the area of the emission in square centimeters (in the image plane at the distance of the source) and J is the average measured radiance in watts per square centimeter per steradian. Power estimates assume emission at the following wavelengths: violet, 404 nm; green, 560 nm; red, 630 nm; and clear, 560 nm. Depending on the actual spectrum, the sum of the power emitted in the red, green, and violet filters may not necessarily equal that in the clear filter [see also (14)].
20. A. P. Ingersoll et al., Icarus 135, 251 (1998).
21. J. T. Clark, J. Ajello, J. Luhmann, N. Schneider, I. Kanik, J. Geophys. Res. 99, 6387 (1994); G. E. Ballester et al., Bull. Am. Astron. Soc. 29, 980 (1997).
22. J. T. Clark, J. Ajello, J. Luhmann, N. Schneider, I. Kanik, J. Geophys. Res. 99, 6387 (1994); G. E. Ballester et al., Bull. Am. Astron. Soc. 29, 980 (1997).
23. A. S. McEwen et al., Icarus 135, 181 (1998).
24. Jupiter is surrounded by a torus-shaped cloud of trapped charged particles that rotate with the planet's magnetic field. The plasma torus is mainly made up of S and O ions and electrons that are continually being replenished by Io. The centrifugal equator of the plasma torus is inclined by ∼7° to Jupiter's equatorial plane, so the torus wobbles with respect to Io's position every 13 hours as Jupiter rotates. Io is at maximum north and south magnetic latitudes (that is, farthest from the plasma torus center) for System III magnetic longitudes of ∼200° and 20°, respectively, and is in the magnetic equator (the densest part of the plasma torus) at ∼110° and 290°, respectively. Embedded within the torus is a narrow vertical band of concentrated plasma known as the "ribbon." The origin of this curious feature is as yet poorly known.
25. See also R. G. Strom and N. M. Schneider, in Satellites of Jupiter, D. Morrison, Ed. (Univ. of Arizona Press, Tucson, AZ, 1982), chap. 16. More realistic hydrodynamic simulations [for example, J. V. Austin and D. B. Goldstein, Bull. Am. Astron. Soc. 30, 1121 (1998)] produce plumes that are somewhat flatter than those shown here, owing to shock pressure and horizontal flow.
26. See also R. G. Strom and N. M. Schneider, in Satellites of Jupiter, D. Morrison, Ed. (Univ. of Arizona Press, Tucson, AZ, 1982), chap. 16. More realistic hydrodynamic simulations [for example, J. V. Austin and D. B. Goldstein, Bull. Am. Astron. Soc. 30, 1121 (1998)] produce plumes that are somewhat flatter than those shown here, owing to shock pressure and horizontal flow.
27. P. Goldreich and D. Lynden-Bell, Astrophys. J. 156, 59 (1969).
28. J. Linker, K. Khurana, M. Kivelson, K. Walker, J. Geophys. Res. 103, 19867 (1998); M. Combi, K. Kabin, T. Gombosi, D. Dezeeuw, K. Powell, ibid., p. 9071; J. Saur, F. M. Neubauer, D. F. Strobel, M. E. Summers, ibid., in press.
29. J. Linker, K. Khurana, M. Kivelson, K. Walker, J. Geophys. Res. 103, 19867 (1998); M. Combi, K. Kabin, T. Gombosi, D. Dezeeuw, K. Powell, ibid., p. 9071; J. Saur, F. M. Neubauer, D. F. Strobel, M. E. Summers, ibid., in press.
30. J. Linker, K. Khurana, M. Kivelson, K. Walker, J. Geophys. Res. 103, 19867 (1998); M. Combi, K. Kabin, T. Gombosi, D. Dezeeuw, K. Powell, ibid., p. 9071; J. Saur, F. M. Neubauer, D. F. Strobel, M. E. Summers, ibid., in press.
31. Possible effects of current flow through Io were described by T. Gold [Science 206, 1071 (1979) ] and A. Peratt and A. Dessler [Astrophys. Space Sci. 144, 451 (1988)].
32. Possible effects of current flow through Io were described by T. Gold [Science 206, 1071 (1979) ] and A. Peratt and A. Dessler [Astrophys. Space Sci. 144, 451 (1988)].
33. J. Pearl et al., Nature 280, 757 (1979); P. Sartoretti et al., Icarus 122, 273 (1996).
34. J. Pearl et al., Nature 280, 757 (1979); P. Sartoretti et al., Icarus 122, 273 (1996).
35. K. Miller and K. Becker, Can. J. Phys. 65, 530 (1987).
36. E. C. Sittler and D. F. Strobel, J. Geophys. Res. 92, 5741 (1987).
37. 2 appropriate to the SSI violet filter was estimated from laboratory measurements (6, 25), with guidance given by K. Becker (private communication).
38. -3 [F. Bagenal, J. Geophys. Res. 99, 11043 (1994)].
39. -3 measured in the plasma torus near Io [D. A. Gurnett, W. S. Kurth, A. Roux, S. J. Bolton, C. F. Kennel, Science 274, 391 (1996); L. A. Frank et al., ibid., p. 394].
40. -3 measured in the plasma torus near Io [D. A. Gurnett, W. S. Kurth, A. Roux, S. J. Bolton, C. F. Kennel, Science 274, 391 (1996); L. A. Frank et al., ibid., p. 394].
41. M. Volwerk, M. Brown, A. Dessler, B. Sandel, Geophys. Res. Lett. 24, 1147 (1997).
42. M. C. Wong and W. H. Smyth, Bull. Am. Astron. Soc. 30, 1117 (1998); in preparation.
43. We are grateful for informative discussions with many patient colleagues before and during the Madison, Wisconsin, meeting of the Division for Planetary Sciences of the American Astronomical Society. Particular thanks are due to C. Alexander, F. Bagenal, F. Crary, A. Dessler, F. Herbert, W. Hubbard, D. Hunten, K. Klaasen, L. Lane, M. McGrath, K. Rages, and N. Schneider.