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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Blanpain, Bart |
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| Ali, M. A. |
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| Popa, V. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Nicholson, P. D.
in Cooperation with on an Cooperation-Score of 37%
Topics
Publications (9/9 displayed)
- 2019Cassini-VIMS observations of Saturn's main rings: II. A spectrophotometric study by means of Monte Carlo ray-tracing and Hapke's theorycitations
- 2017From the Icy Satellites to Small Moons and Rings: Spectral Indicators by Cassini-VIMS Unveil Compositional Trends in the Saturnian System
- 2015Studies of Saturn's Main Rings at Multiple Wavelengths
- 2013Surface Composition of the Non-Ice Component on Icy Satellites and Ring Particles in the Saturn System
- 2012Multi-wavelength studies of Saturn's rings to constrain ring particle properties and ring structure: the VIMS perspective
- 2011Composition and Grain Sizes of Dark Material in Saturn's Icy Satellites and Rings
- 2011The Composition of Saturn's Rings and Satellites from Cassini VIMS and UVIS
- 2008The Composition of Saturn's Rings
- 2007Saturn's Rings Observed with Cassini-VIMS
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document
The Composition of Saturn's Rings
Abstract
The Cassini spacecraft has obtained a unique collection of data about Saturn's rings, as it has observed the rings from 0 to 180 degrees in phase angle, and on both lit and unlit sides. Identification of trace contaminants, especially organic compounds, requires that spectra of the rings be uncontaminated by light from Saturn. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) has acquired 0.35 to 5.1 micron, high spatial resolution spectroscopic data near the shadow of Saturn on the rings where scattered light is at a minimum. At low phase angles, the ring spectra show classic crystalline-ice spectral features except for a contaminant causing a UV absorption. VIMS spectra at 180-degree phase angle are generally flat, with only a weak positive feature at 2.86 microns in spectra of the F-ring. The general transmission decrease is due to large ring particles completely blocking light. The 2.86-micron feature indicates the presence of fine ice dust, where the ice's index of refraction is near 1.0, and light is not refracted or diffracted. There are no indications of interparticle scattering in the VIMS data at any phase angle. The lack of interparticle scattering indicates that the dense A and B rings must be very thin, approaching a monolayer, but rigorous constraints have yet to be modeled. Previous studies used tholins and amorphous carbon for the contaminant causing the UV absorption, but these models display additional absorptions and spectral structure in the near infrared not seen in VIMS data. Clark et al. (Icarus, v193, p372, 2008) modeled the changing blue peak and UV absorber observed on Phoebe, Iapetus, Hyperion, and Dione with amorphous carbon and nano-sized hematite. Nanohematite has muted spectral features compared to larger grained hematite, due to crystal field effects at the surfaces of small grains. Nanohematite has a strong UV absorber that matches the steep UV slope observed in spectra of Saturn's rings and has no strong IR absorptions. If the UV absorber in Saturn's rings is due to nanophase hematite then less than 1% hematite would be required, if it is uniformly mixed within the ice grains of the ring particle regoliths. <P />...