The Dust Halo of Saturn's Largest Icy Moon, Rhea
Abstract
Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.
Get full access to this article
View all available purchase options and get full access to this article.
Already a Subscriber?Sign In
Supplementary Material
File (jones_som.pdf)
References and Notes
1
A. V. Krivovet al., Planet. Space Sci.51, 251 (2003).
2
M. Sremcevic, A. V. Krivov, F. Spahn, Planet. Space Sci.51, 455 (2003).
3
J. F. Carbary, S. M. Krimigis, W.-H. Ip, J. Geophys. Res.88, 8947 (1983).
4
Materials, methods, and further discussion are available as supporting material on Science Online.
5
G. H. Joneset al., Science311, 1412 (2006).
6
R. Sramaet al., Space Sci. Rev.114, 465 (2004).
7
J. Saur, D. F. Strobel, Astrophys. J.620, L115 (2005).
8
L. W. Espositoet al., Space Sci. Rev115, 299 (2004).
9
M. F. Thomsen, J. A. Van Allen, J. Geophys. Res.85, (A11), 5831 (1980).
10
National Institute of Standards and Technology Physical Reference Data, http://physics.nist.gov/PhysRefData/, (2006).
11
J. N. Cuzzi, J. A. Burns, Icarus74, 284 (1988).
12
P. C. Birch, S. Chapman, Phys. Plasmas9, 1785 (2002).
13
T. J. Stubbset al., abstr. 1899, Lunar and Planetary Science Conference XXXVI, Lunar and Planetary Institute (League City, TX, 14 to 18March2005).
14
S. Kempfet al., Planet. Space Sci.54, 999 (2006).
15
Test particles were inserted into a wide range of simulated orbits about Rhea in the restricted three-body problem framework (17). Over >35,000 Saturnian years, semimajor axis, eccentricity, and inclination perturbations were remarkably restricted, as found in other contexts (18). Most <30° inclination particles survived the full, 106-year integration period if initial pericentres permitted small eccentricity excursions. Particles at the brief electron dropouts' distances were largely unperturbed. Overall stability was unchanged over a separate, 105-year integration that additionally included Titan's presence and Saturn's oblateness (4).
16
R. J. Wagneret al., Lunar and Planetary Science Conference XXXVIII, abstr. 1958, Lunar and Planetary Institute (League City, TX, 12 to 16March2007).
17
E. Everhart, in Dynamics of Comets: Their Origin and Evolution, A. Carusi, B. Valsecchi, Eds. (D. Reidel, Dordrecht, Netherlands, 1985), pp. 185–202.
18
D. P. Hamilton, J. A. Burns, Icarus92, 118 (1991).
19
S. M. Krimigiset al., Space Sci. Rev.114, 233 (2004).
20
D. T. Younget al., Space Sci. Rev.114, 1 (2004).
21
D. A. Gurnettet al., Space Sci. Rev.114, 395 (2004).
22
M. K. Doughertyet al., Space Sci. Rev.114, 331 (2004).
23
K. K. Khurana, C. T. Russell, M. K. Dougherty, Icarus192, 465 (2008).
24
W. S. Kurthet al., Planet. Space Sci.54, 988 (2006).
25
E. Roussoset al., Icarus193, 455 (2008).
26
Cassini-Huygens is a mission of international collaboration between NASA, the European Space Agency (ESA), and the Agenzia Spaziale Italiana (ASI). We thank M. Kusterer (The Johns Hopkins University Applied Physics Laboratory, JHUAPL), N. Achilleos, and S. Kellock (Imperial College London) for data reduction. MIMI/LEMMS was partly financed by the German Bundesministerium für Bildung und Forschung through the German Aerospace Center (DLR) and by the Max Planck Gesellschaft. Work at JHUAPL, Johns Hopkins University, University of Iowa, and Southwest Research Institute was supported by NASA, as was that at Los Alamos National Laboratory, under the auspices of the U.S. DOE. Work at University College London and Imperial College London was supported by the U.K. Science and Technology Facilities Council. We acknowledge suggestions by T. V. Johnson and discussions with N. André and J. Schmidt.
Information & Authors
Information
Published In
Science
Volume 319 • Issue 5868 • 7 March 2008
Pages: 1380 - 1384
History
Received: 9 October 2007
Accepted: 1 February 2008
Copyright
American Association for the Advancement of Science.
