Advertisement

Abstract

NASA's Galileo mission to Jupiter and improved Earth-based observing capabilities have allowed major advances in our understanding of Jupiter's moons Io, Europa, Ganymede, and Callisto over the past few years. Particularly exciting findings include the evidence for internal liquid water oceans in Callisto and Europa, detection of a strong intrinsic magnetic field within Ganymede, discovery of high-temperature silicate volcanism on Io, discovery of tenuous oxygen atmospheres at Europa and Ganymede and a tenuous carbon dioxide atmosphere at Callisto, and detection of condensed oxygen on Ganymede. Modeling of landforms seen at resolutions up to 100 times as high as those of Voyager supports the suggestion that tidal heating has played an important role for Io and Europa.

Get full access to this article

View all available purchase options and get full access to this article.

REFERENCES AND NOTES

1
G. Schubert, T. Spohn, R. T. Reynolds, in Satellites (Univ. of Arizona Press, Tucson, AZ, 1986), pp. 224–292.
2
D. J. Stevenson, A. W. Harris, J. I. Lunine, in Satellites (Univ. of Arizona Press, Tucson, AZ, 1986), pp. 39–88.
3
D. B. Nash, M. H. Carr, J. Gradie, D. M. Hunten, C. F. Yoder, in Satellites (Univ. of Arizona Press, Tucson, AZ, 1986), pp. 629–688.
4
B. K. Lucchitta and L. A. Soderblom, in Satellites of Jupiter (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 521–555; M. C. Malin and D. C. Pieri, in Satellites (Univ. of Arizona Press, Tucson, AZ, 1986), pp. 689–717.
5
W. B. McKinnon and E. M. Parmentier, in Satellites (Univ. of Arizona Press, Tucson, AZ, 1986), pp. 718–763.
6
Smith B. A., et al., Science 204, 951 (1979);
Smith B. A., et al., 206, 927 (1979);
. See (10) for an opposing view on possible early volcanism on Callisto.
7
Peale S. J., Annu. Rev. Astron. Astrophys. 37, 37 (1999).
8
See special issue of Space. Sci. Rev. 60 (nos. 1 to 4) (1992) for instrument descriptions.
9
P. M. Schenk, J. Geophys. Res. 96, 15,635 (1991); ibid. 98, 7475 (1993).
10
___, 100, 19023 (1995).
11
Calvin W. M., Clark R. N., Icarus 104, 69 (1993).
12
Spencer J. R., 70, 99 (1987).
13
Calvin W. M., Clark R. N., Brown R. H., Spencer J. R., J. Geophys. Res. 100, 19041 (1995).
14
Anderson J. D., et al., Science 280, 1573 (1998).
15
Three-layer models containing an iron core cannot match the data, but a four-layer model containing an iron core, silicate mantle, mixed rock and ice mantle, and outermost ice layer has not been investigated and might fit the observations.
16
McKinnon W. B., Icarus 130, 540 (1997);
. However, evidence that Europa and Ganymede are nearly hydrostatic suggests caution in adopting this alternative. At the other extreme, a factor of two variation in the assumed rock/ice ratio of accreting planetesimals would allow the moment of inertia to be consistent with an undifferentiated Callisto.
17
Kivelson M. G., et al., J. Geophys. Res. 104, 4609 (1999);
; K. K. Khurana et al. Nature 395, 777 (1998).
18
An ionosphere can also potentially provide conductivity, but the high electron densities required and the typically patchy nature of ionospheres suggest that this is unlikely.
19
Kargel J. S., Icarus 100, 556 (1992).
20
___, 94, 368 (1991);
; D. L. Hogenboom, J. S. Kargel, J. P. Ganasan, L. Lee, ibid. 115, 258 (1995); D. L. Hogenboom, J. S. Kargel, P. V. Pahalawatta, Lunar Planet. Sci. Conf.XXX (1999) [CD-ROM].
21
Callisto might have accreted some ammonia hydrates, although quantification is difficult [
Lunine J. I., Stevenson D. J., Icarus 52, 14 (1982);
]. A 10-km-thick ocean would have eutectic composition (hence substantial freezing point depression) if it froze from a 400-km liquid layer containing an NH3/H2O mole fraction of ∼0.01 (∼10% solar). Complete freezing of such an ocean would be prevented because convective heat loss in the overlying ice would be negligible close to the lowered freezing temperature [
Kirk R. L., Stevenson D. J., Icarus 69, 91 (1987)].
22
Friedson A. J., Stevenson D. J., Icarus 56, 1 (1983).
23
McCord T. B., et al., J. Geophys. Res. 103, 8603 (1998);
McCord T. B., et al., Science 278, 271 (1997).
24
Carlson R., et al., 274, 385 (1996).
25
Delitsky M. L., Lane A. L., J. Geophys. Res. 103, 31391 (1998).
26
Noll K. S., Johnson R. E., McGrath M. A., Caldwell J. J., Geophys. Res. Lett. 24, 1139 (1997);
; A. L. Lane, D. L. Domingue, ibid., p. 1143.
27
Carlson R. W., Science 283, 820 (1999).
28
Johnson R. E., Killen R. M., Waite J. H., Lewis W. S., Geophys. Res. Lett. 25, 3257 (1998).
29
J. M. Moore et al., Icarus, in press.
30
Prockter L. M., et al., 135, 317 (1998).
31
A. Woronow, R. G. Strom, M. Gurnis, in Satellites of Jupiter (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 237–276. Unpublished images from Galileo's 21st orbit hint that small craters may not be depleted in all locations.
32
Moore J. M., Mellon M. T., Zent A. P., Icarus 122, 63 (1996).
33
Zahnle K., Dones L., Levison H. F., 136, 202 (1998).
34
Anderson J. D., Lau E. L., Sjogren W. L., Schubert G., Moore W. B., Nature 384, 541 (1996).
35
Belton M. J. S., et al., Science 274, 377 (1996).
36
Pappalardo R. T., et al., Icarus 135, 276 (1998).
37
Collins G. C., Head J. W., Pappalardo R. T., Geophys. Res. Lett. 25, 233 (1998).
38
R. T. Pappalardo and G. C. Collins, Lunar Planet. Sci. Conf. XXX (1999) [CD-ROM].
39
M. P. Golombek, J. Geophys. Res. 87 (suppl.), A77 (1982);
Parmentier E. M., Squyres S. W., Head J. W., Allison M. L., Nature 295, 290 (1982).
40
J. W. Head III et al., Lunar Planet. Sci. Conf. XXX (1999) [CD-ROM].
41
J. W. Head III et al., ibid.XXIX (1998) [CD-ROM].
42
Showman A. P., Stevenson D. J., Malhotra R., Icarus 129, 367 (1997).
43
Topographic lows within grooved terrain are generally three times darker than the topographic highs (36). A possible cause is sloughing of a dark veneer into topographic lows during tectonism, which might expose underlying bright ice and thereby explain the brightening, although the idea remains qualitative.
44
J. Patel et al., J. Geophys. Res., in press.
45
A necking instability refers to runaway pinching (or “necking”) of thin lithospheric regions during lithospheric extension. This mechanism was evaluated as unlikely during the Voyager era, but new rheological data for ice have prompted a reanalysis, indicating that the mechanism may indeed be feasible. See (37);
Herrick D. L., Stevenson D. J., Icarus 85, 191 (1990);
; A. J. Dombard and W. B. McKinnon, in preparation.
46
Collins G. C., Head J. W., Pappalardo R. T., Icarus 135, 345 (1998);
. The complexity of the tectonized terrains seen by Galileo and the need to extrapolate patterns to low-resolution Voyager images argue for caution in adopting a given stratigraphy, although the coherence of the inferred stress pattern does lend the proposed stratigraphy credence.
47
Showman A. P., Malhotra R., Icarus 127, 93 (1997);
Malhotra R., 94, 399 (1991).
48
Tittemore W. C., Science 250, 263 (1990);
Greenberg R., Icarus 70, 334 (1987).
49
Goldreich P., Soter S., Icarus 5, 375 (1966).
50
M. G. Kivelson et al., J. Geophys. Res. 103, 19,963 (1998);
Kivelson M. G., et al., Geophys. Res. Lett. 24, 2155 (1997);
Kivelson M. G., et al., Nature 384, 537 (1996).
51
Gurnett D. A., Kurth W. S., Roux A., Bolton S. J., Kennel C. F., Nature 384, 535 (1996).
52
Williams D. J., Mauk B., McEntire R. W., J. Geophys. Res. 103, 17523 (1998);
Williams D. J., et al., Geophys. Res. Lett. 24, 2163 (1997).
53
Frank L. A., Paterson W. R., Ackerson K. L., Bolton S. J., Geophys. Res. Lett. 24, 2159 (1997).
54
W. S. Kurth, D. A. Gurnett, A. Roux, S. J. Bolton, ibid., p. 2167.
55
Schubert G., Zhang K., Kivelson M. G., Anderson J. D., Nature 384, 544 (1996).
56
Z. Kuang and D. J. Stevenson, Eos 77(fall meet. suppl.), F437 (1996).
57
The resonance must heat the core and silicate mantle to a high enough temperature that, when the resonance ends, the cooling (which is largely controlled by the silicate mantle temperature) exceeds the required value. However, the ancient resonances that have been proposed (47) can generate only ∼1011 W of mean tidal heating within the silicate layer, ∼20% of current radiogenic heat production. This value is insufficient to cause a major heating of the core. Scenarios in which the heat is deposited episodically should be considered, but it is unclear that they will get around the fact that the total resonant heat budget is modest.
58
Crary F. J., Bagenal F., J. Geophys. Res. 103, 25757 (1998).
59
Spencer J. R., Calvin W. M., Person M. J., 100, 19049 (1995);
Calvin W. M., Spencer J. R., Icarus 130, 505 (1997).
60
Noll K. S., Johnson R. E., Lane A. L., Domingue D. L., Weaver H. A., Science 273, 341 (1996).
61
Hendrix A. R., Barth C. A., Hord C. W., J. Geophys. Res. 104, 14169 (1999).
62
Calvin W. M., Johnson R. E., Spencer J. R., Geophys. Res. Lett. 23, 673 (1996);
Vidal R. A., Bahr D., Baragiola R. A., Peters M., Science 276, 1839 (1997);
; M. T. Sieger, W. C. Simpson, T. M. Orlando, Nature 394, 554 (1998);
Baragiola R. A., Bahr D. A., J. Geophys. Res. 103, 25865 (1998);
Johnson R. E., 104, 14179 (1999);
; R. A. Baragiola, C. L. Atteberry, D. A. Bahr, M. Peters, ibid., p. 14183.
63
Johnson R. E., Jesser W. A., Astrophys. J. 480, L79 (1997).
64
Hall D. T., Feldman P. D., McGrath M. A., Strobel D. F., 499, 475 (1998).
65
Barth C. A., et al., Geophys. Res. Lett. 24, 2147 (1997);
; L. A. Frank, W. R. Paterson, K. L. Acherson, S. J. Bolton, ibid., p. 2151.
66
Domingue D. L., Lane A. L., Beyer R. A., 25, 3117 (1998).
67
Lane A. L., Nelson R. M., Matson D. L., Nature 292, 38 (1981);
Ockert M., Nelson R., Lane A., Matson D., Icarus 70, 499 (1987);
Buratti B., Golombek M., 75, 437 (1988).
68
Reynolds R. T., Cassen P. M., Geophys. Res. Lett. 6, 121 (1979);
; P. M. Cassen, S. J. Peale, R. T. Reynolds, in Satellites of Jupiter (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 93–128.
69
Cassen P., Reynolds R. T., Peale S. J., Geophys. Res. Lett. 6, 731 (1979);
Cassen P., Peale S. J., Reynolds R. T., ibid 7, 987 (1980);
Squyres S. W., Reynolds R. T., Cassen P. M., Peale S. J., Nature 301, 225 (1983) ;
Ojakangas G. W., Stevenson D. J., Icarus 81, 220 (1989).
70
Anderson J. D., et al., Science 281, 2019 (1998);
Anderson J. D., Lau E. L., Sjogren W. L., Schubert G., Moore W. B., 276, 1236 (1997).
71
Greeley R., et al., Icarus 135, 4 (1998).
72
P. E. Geissler et al., ibid., p. 107.
73
Carr M. H., et al., Nature 391, 363 (1998);
Spaun N. A., Head J. W., Collins G. C., Prockter L. M., Pappalardo R. T., Geophys. Res. Lett. 25, 4277 (1998).
74
R. Greenberg et al., Icarus, in press.
75
Greenberg R., et al., 135, 64 (1998).
76
Sullivan R., et al., Geol. Soc. Am. Abstr. Program 29, A312 (1997).
77
Crawford G. D., Stevenson D. J., Icarus 73, 66 (1988).
78
J. W. Head et al., Lunar Planet. Sci. Conf. XXIX (abstract 1414), (1998) [CD-ROM].
79
S. A. Fagents, R. Greeley, R. J. Sullivan, R. T. Pappalardo, L. M. Prockter, in preparation.
80
Williams K. K., Greeley R., Geophys. Res. Lett. 25, 4273 (1998).
81
R. T. Pappalardo et al., J. Geophys. Res., in press.
82
Pappalardo R. T., et al., Nature 391, 365 (1998).
83
McKinnon W. B., Geophys. Res. Lett. 26, 951 (1999).
84
Leith A. C., McKinnon W. B., Icarus 120, 387 (1996);
Helfenstein P., Parmentier E. M., 61, 175 (1985);
McEwen A. S., Nature 321, 49 (1986).
85
Geissler P. E., et al., Nature 391, 368 (1998).
86
Hoppa G., et al., Icarus 137, 341 (1999).
87
C. B. Phillips et al., in preparation.
88
Noll K. S., Weaver H. A., Gonnella A. M., J. Geophys. Res. 100, 19057 (1995).
89
Domingue D. L., Lane A. L., Geophys. Res. Lett. 25, 4421 (1998).
90
Carlson R. W., et al., Science 283, 2062 (1999).
91
McCord T. B., et al., J. Geophys. Res. 104, 11827 (1999);
McCord T. B., et al., Science 280, 1242 (1998);
Carlson R. W., Johnson R. E., Anderson M. S., Science 286, 97 (1999).
92
Clark B. E., et al., Icarus 135, 95 (1998).
93
Hall D. T., Strobel D. F., Feldman P. D., McGrath M. A., Weaver H. A., Nature 373, 677 (1995).
94
Brown M. E., Hill R. E., 380, 229 (1996).
95
Kliore A. J., Hinson D. P., Flasar F. M., Nagy A. F., Cravens T. E., Science 277, 355 (1997);
Saur J., Strobel D. F., Neubauer F. M., J. Geophys. Res. 103, 19947 (1998).
96
Paranicas C., Cheng A. F., Williams D. J., J. Geophys. Res. 103, 15001 (1998).
97
Sullivan R., et al., Nature 391, 371 (1998);
Pappalardo R. T., Sullivan R. J., Icarus 123, 557 (1996);
Schenk P. M., McKinnon W. B., 79, 75 (1989).
98
Moore J. M., et al., Icarus 135, 127 (1998);
; E. P. Turtle, C. P. Phillips, A. S. McEwen, J. M. Moore, R. Greeley, Lunar. Planet. Sci. Conf. XXIX (1998) [CD-ROM]. The impact structures allegedly associated with puncture through the lithosphere are extremely flat at the scale of the whole feature, often contain several concentric ridges or troughs, and lack raised rims, central peaks, and central pits characteristic of craters formed by impact into solid ice or rock.
99
Spencer J. R., Schneider N. M., Annu. Rev. Earth Planet. Sci. 24, 125 (1996).
100
M. Küppers and N. M. Schneider, in preparation.
101
Spencer J. R., et al., Icarus 127, 221 (1997);
Moses J. I., Nash D. B., 89, 277 (1991);
; A. S. McEwen, ibid.73, 385 (1988);
Steudel R., et al., J. Geophys. Res. 91, 4971 (1986).
102
J. C. Pearl and W. M. Sinton, in Satellites of Jupiter, D. Morrison, Ed. (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 724–755.
103
Carr M. H., J. Geophys. Res. 91, 3521 (1986).
104
McEwen A. S., et al., Science 281, 87 (1998);
McEwen A. S., et al., Icarus 135, 181 (1998);
Spencer J. R., et al., Geophys. Res. Lett. 24, 2451 (1997).
105
Carr M. H., et al., Icarus 135, 141 (1998);
Schenk P. M., Bulmer M. H., Science 279, 1514 (1998).
106
Veeder G. J., et al., J. Geophys. Res. 99, 17095 (1994).
107
Blaney D. L., et al., Icarus 113, 220 (1995);
Blaney D. L., et al., Geophys. Res. Lett. 24, 2459 (1997).
108
R. Greenberg, in Satellites of Jupiter, D. Morrison, Ed. (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 65–92;
Ojakangas G. W., Stevenson D. J., Icarus 66, 341 (1986) .
109
Ioannou P. J., Lindzen R. S., Astrophys. J. 406, 266 (1993).
110
Anderson J. D., Sjogren W. L., Schubert G., Science 272, 709 (1996).
111
Thomas P. C., et al., Icarus 135, 175 (1998).
112
Kivelson M. G., et al., Science 273, 337 (1996).
113
Weinbruch U., Spohn T., Planet. Space Sci 43, 1045 (1995);
Sarson G. R., Jones C. A., Zhang K., Schubert G., Science 276, 1106 (1997);
Sarson G. R., Jones C. A., Zhang K., Phys. Earth Planet. Inter. 111, 47 (1999).
114
Kerswell R. R., Malkus W. V. R., Geophys. Res. Lett. 25, 603 (1998).
115
Frank L. A., et al., Science 274, 394 (1996);
Linker J. A., Khurana K. K., Kivelson M. G., Walker R. J., J. Geophys. Res. 103, 19867 (1998).
116
Lellouch E., Icarus 124, 1 (1996).
117
Roesler F. L., et al., Science 283, 353 (1999);
Geissler P. E., et al., 285, 870 (1999).
118
The detailed dynamics, including transport processes and energy flow within the plasma torus, constitute a large subject beyond the scope of the present article; the reader is referred to (99) and F. J. Crary et al. [J. Geophys. Res. 103, 29359 (1998)] for recent results.
119
D. J. Stevenson, in Europa Ocean Conference (San Juan Institute, San Juan Capistrano, CA, 1996), pp. 69–70.
120
Davies M. E., et al., Icarus 135, 372 (1998).
121
Neubauer F. M., J. Geophys. Res. 103, 19843 (1998).
122
We thank T. E. Dowling, W. B. McKinnon, R. T. Pappalardo, P. Schenk, N. Schneider, J. Spencer, J. Stansberry, and D. J. Stevenson for discussions. This work was supported by NASA.

(0)eLetters

eLetters is a forum for ongoing peer review. eLetters are not edited, proofread, or indexed, but they are screened. eLetters should provide substantive and scholarly commentary on the article. Embedded figures cannot be submitted, and we discourage the use of figures within eLetters in general. If a figure is essential, please include a link to the figure within the text of the eLetter. Please read our Terms of Service before submitting an eLetter.

Log In to Submit a Response

No eLetters have been published for this article yet.

Information & Authors

Information

Published In

Science
Volume 286 | Issue 5437
1 October 1999

Submission history

Published in print: 1 October 1999

Permissions

Request permissions for this article.

Authors

Affiliations

Adam P. Showman [email protected]
Department of Mechanical Engineering, University of Louisville, 215 Sackett Hall, Louisville, KY 40292, USA. E-mail: [email protected]
and Renu Malhotra [email protected]
Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058, USA. E-mail: [email protected]

Metrics & Citations

Metrics

Article Usage

Altmetrics

Citations

Cite as

Export citation

Select the format you want to export the citation of this publication.

Cited by

  1. Planetary Science--A Space Odyssey, Science, 287, 5455, (997-1005), (2021)./doi/10.1126/science.287.5455.997
    Abstract
  2. Gravity Field, Shape, and Moment of Inertia of Titan, Science, 327, 5971, (1367-1369), (2021)./doi/10.1126/science.1182583
    Abstract
  3. Jupiter and Its Moons, Science, 294, 5540, (71-72), (2001)./doi/10.1126/science.1065306
    Abstract
Loading...

View Options

Check Access

Log in to view the full text

AAAS ID LOGIN

AAAS login provides access to Science for AAAS Members, and access to other journals in the Science family to users who have purchased individual subscriptions.

Log in via OpenAthens.
Log in via Shibboleth.

More options

Purchase digital access to this article

Download and print this article for your personal scholarly, research, and educational use.

Purchase this issue in print

Buy a single issue of Science for just $15 USD.

View options

PDF format

Download this article as a PDF file

Download PDF

Full Text

FULL TEXT

Media

Figures

Multimedia

Tables

Share

Share

Share article link

Share on social media