Amalthea's Density Is Less Than That of Water

Anderson, J. D.; Johnson, T. V.; Schubert, G.; Asmar, S. W.; Jacobson, R. A.; Johnston, D. V.; Lau, E. L.; Lewis, G. D.; Moore, W. B.; Taylor, Anthony H.; Thomas, P. C.; Weinwurm, G.

doi:10.1126/science.1110422

Cited by 69 publications

(53 citation statements)

References 13 publications

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“…The dust is transported radially inward by PR drag, while orbital and Lorentz resonances sculpt the ring's appearance. Amalthea's low bulk density of 0.86 ± 0.1 g cm −3 (Anderson et al 2005) suggests a high porosity (30-70%; unless it is mostly composed of water ice). Such a high porosity hints at a violent collisional history.…”

Section: Discussionmentioning

confidence: 99%

Keck observations of the 2002–2003 jovian ring plane crossing

Pater¹,

Showalter²,

Macintosh³

2008

Icarus

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We present new observations of Jupiter's ring system at a wavelength of 2.2 µm obtained with the 10-m W. M. Keck telescopes on three nights during a ring plane crossing: UT 19 December 2002, and 22 and 26 January 2003. We used conventional imaging, plus adaptive optics on the last night. Here we present detailed radial profiles of the main ring, halo and gossamer rings, and interpret the data together with information extracted from radio observations of Jupiter's synchrotron radiation. The main ring is confined to a 800-km-wide annulus between 128,200 and 129,000 km, with a ∼ 5000 km extension on the inside. The normal optical depth is 8 × 10 −6 , 15% of which is provided by bodies with radii a > ∼ 5 cm. These bodies are as red as Metis. Half the optical depth, τ ≈ 4 × 10 −6 , is attributed to micron-sized dust, and the remaining τ ≈ 3 × 10 −6 to grains tens to hundreds of µm in size. The inward extension consists of micron-sized (a < ∼ 10 µm ) dust, which probably migrates inward under Poynting-Robertson drag. The inner limit of this extension falls near the 3:2 Lorentz resonance (at orbital radius r = 122, 400 km), and coincides with the outer limit of the halo. The gossamer rings appear to be radially confined, rather than broad sheets of material. The Amalthea ring is triangularly shaped, with a steep outer dropoff over ∼5000 km, extending a few 1000 km beyond the orbit of Amalthea, and a more gradual inner dropoff over 15,000-20,000 km. The inner edge is near the location of the synchronous orbit. The optical depth in the Amalthea ring is ∼ 5×10 −7 , up to 20% of which is comprised of macroscopic material. The optical depth in the Thebe ring is a factor of 3 smaller.

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Section: Discussionmentioning

confidence: 99%

Keck observations of the 2002–2003 jovian ring plane crossing

Pater¹,

Showalter²,

Macintosh³

2008

Icarus

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“…Canup and Ward 2002;Mousis and Gautier 2004). However, the discovery that Amalthea, a small regular moon orbiting closer to Jupiter than Io, had a higher ice-to-rock ratio than the Galilean satellites (Anderson et al 2005) challenged this assumption. This discovery brought about the possibility that all of the Jovian moons could have accreted significant amounts of ice, and that subsequent heating-either tidal heating or bombardment-could have driven off much of the water ice from Io and Europa (Estrada et al 2009).…”

Section: The Galilean Satellitesmentioning

confidence: 95%

“…This discovery brought about the possibility that all of the Jovian moons could have accreted significant amounts of ice, and that subsequent heating-either tidal heating or bombardment-could have driven off much of the water ice from Io and Europa (Estrada et al 2009). However, this does not rule out the possibility that Amalthea formed later than the giant satellites or in a colder region of the subnebula and migrated to its current location (Anderson et al 2005).…”

Section: The Galilean Satellitesmentioning

confidence: 99%

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

et al. 2015

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Comets play a dual role in understanding the formation and evolution of the solar system. First, the composition of comets provides information about the origin of the giant planets and their moons because comets formed early and their composition is not expected to have evolved significantly since formation. They, therefore serve as a record of conditions during the early stages of solar system formation. Once comets had formed, their orbits were perturbed allowing them to travel into the inner solar system and impact the planets. In this way they contributed to the volatile inventory of planetary atmospheres. We review here how knowledge of comet composition up to the time of the Rosetta mission has contributed to understanding the formation processes of the giant planets, their moons and small icy bodies in the solar system. We also discuss how comets contributed to the volatile inventories of the giant and terrestrial planets.

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“…Amalthea which has a density as small as 0.86 g cm −3 (Anderson et al, 2005) could be the remnant of such a process. It could have been pushed outward because of the tidal effect.…”

Section: Thick Disk Vs Narrow Ringsmentioning

confidence: 99%

The Jovian Rings

2010

Proc. IAU

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Abstract.A comparison of the Jovian and Saturnian rings is made by reviewing the recent advances in planetary spacecraft exploration and theoretical study. Two main issues are addressed, namely, the different structures of these two planetary ring systems and the water ice composition of the Saturnian rings. It is suggested that answers might be found by invoking tidal capture of Trans-Neptunian Objects with highly differentiated structures even though catastrophic breakup of pre-existing satellites in the ring regions remains a real possibility. Erosion mechanisms such as meteoroid impact, photo-sputtering, orbital instability of charged dust particles and thermal evaporation acting at different time scales could lead to the preservation of the Saturnian ring system but not the Jovian ring system of large mass originally.

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Amalthea's Density Is Less Than That of Water

Cited by 69 publications

References 13 publications

Keck observations of the 2002–2003 jovian ring plane crossing

Keck observations of the 2002–2003 jovian ring plane crossing

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

The Jovian Rings

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