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Metallic Iron and Iron Oxide as an Explanation for the Dark Material Observed on Saturn's Icy Satellites and Rings with Cassini VIMS

Clark, R. N. and Cruikshank, D. P. and Jaumann, Ralf and Brown, Robert H. and Dalle Ore, C. and Stephan, K. and Hoefen, T.M. and Curchin, J. and Buratti, B.J. and Filacchione, G. and Baines, K. H. and Nicholson, P. D. (2010) Metallic Iron and Iron Oxide as an Explanation for the Dark Material Observed on Saturn's Icy Satellites and Rings with Cassini VIMS. In: AAS (Vol. 42). DPS-Meeting, 03.10. - 08.10.10, Pasadena, USA.

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Abstract

The Visual and Infrared Mapping Spectrometer (VIMS) on Cassini has obtained spatially resolved spectra on satellites of Saturn. The Cassini Rev 49 Iapetus fly-by on September 10, 2007, provided data on both the dark material and the transition zone between the dark material and the visually bright ice. The dark material has low albedo with a linear increase in reflectance with wavelength, 3-micron water, and CO2 absorptions. The transition between bright and dark regions shows mixing with unusual optical properties including increased blue scattering and increasing strength of a UV absorber in areas with stronger ice absorptions. Similar spectral effects are observed on other Saturnian satellites and in the rings. We have been unable to match these spectral properties and trends using tholins and carbon compounds. However, the dark material is spectrally matched by fine-grained metallic iron plus nano-phase hematite and adsorbed water which contribute UV and 3-micron absorption, respectively. The blue scattering peak and UV absorption can be explained by Rayleigh scattering from sub-micron particles with a UV absorption, or a combination of Rayleigh scattering and Rayleigh absorption as has been attributed to spectral properties of the Moon. A new radiative transfer model that includes Rayleigh scattering and Rayleigh absorption has been constructed. Models of ice, sub-micron metallic iron, hydrated iron oxide, and trace CO2 explain the observed spectra. Rayleigh absorption requires high absorption coefficient nano-sized particles, which is also consistent with metallic iron. The UV absorber appears to have increased strength on satellite surfaces close to Saturn, with a corresponding decrease in metallic iron signature. A possible explanation is that the iron is oxidized closer to Saturn by oxygen in the extended atmosphere of Saturn's rings, or the dark material is simply covered by clean fine-grained ice particles, for example, from the E-ring. --------------------------------------------------------------------------------

Item URL in elib:https://elib.dlr.de/73063/
Document Type:Conference or Workshop Item (UNSPECIFIED)
Title:Metallic Iron and Iron Oxide as an Explanation for the Dark Material Observed on Saturn's Icy Satellites and Rings with Cassini VIMS
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Clark, R. N.US Geological Survey, Denver, CO, USAUNSPECIFIED
Cruikshank, D. P.NASA Ames Research Center, Moffett Field, CA, USAUNSPECIFIED
Jaumann, Ralfralf.jaumann (at) dlr.deUNSPECIFIED
Brown, Robert H.Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USAUNSPECIFIED
Dalle Ore, C.NASA AmesUNSPECIFIED
Stephan, K. katrin.stephan (at) dlr.deUNSPECIFIED
Hoefen, T.M.US Geological Survey, Denver, CO, USAUNSPECIFIED
Curchin, J.US Geological SurveyUNSPECIFIED
Buratti, B.J.Jet Propulsion Laboratory, Pasadena, CAUNSPECIFIED
Filacchione, G.INAF-IASF, Rome, ItalyUNSPECIFIED
Baines, K. H.Jet Propulsion Laboratory, Pasadena, CA, USAUNSPECIFIED
Nicholson, P. D.Department of Astronomy, Cornell University, Ithaca, NY, USAUNSPECIFIED
Date:2010
Journal or Publication Title:AAS
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Cassini, Saturn, VIMS
Event Title:DPS-Meeting
Event Location:Pasadena, USA
Event Type:international Conference
Event Dates:03.10. - 08.10.10
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Vorhaben CASSINI (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Geology
Deposited By: Stephan, Dr.rer.nat. Katrin
Deposited On:19 Dec 2011 09:25
Last Modified:19 Dec 2011 09:25

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