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Water ice abundance and CO2 band strength on the saturnian satellite Phoebe from Cassini/VIMS observations

Hansen, G. B. and Hollenbeck, E.C. and Stephan, K. and Apple, S.K. and Shin-White, E.-J., C. (2012) Water ice abundance and CO2 band strength on the saturnian satellite Phoebe from Cassini/VIMS observations. Icarus: International Journal of Solar System Studies, 220 (2), pp. 331-338. Elsevier. doi: 10.1016/j.icarus.2012.05.004.

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We have studied the near-infrared spectrum of the Saturn satellite Phoebe, a distant satellite observed before Cassini’s Saturn orbit insertion, using data from the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini orbiter. We have done a critical calibration of the dataset that involves careful correction of dark artifacts. We model areally mixed water ice and non-ice (assumed segregated because of the low ∼3% albedo of the non-ice material) for several high and medium resolution observations of Phoebe made near closest approach. Using a Hapke roughness factor of 15°, we find ice abundances from ∼0.1% to over 4%. The ice grain radii vary from 1 to 10 μm. These are displayed on a projected map of Phoebe with about 50% coverage (about 33% coverage at better than 5 km spatial resolution). Detailed looks at the water ice spectral fits shows that the weak 1.05 and 1.25-μm bands are missing in most of the spectra, implying that the ice endmember is not pure ice, but has a dark material mixed with it that lowers the albedo and suppresses these bands. We made a model of ice contaminated with Phoebe-like dark material showing that a few percent of dark material lowers the albedo to ∼50% and suppresses the bands. The dirty ice model produces better fits to the spectra and implies that the amount of dirty ice is about 1.5 times the amount of pure ice. We have also calculated the CO2 band depth for these same observations and projected the results. The CO2 band depth varies inversely with water ice abundance.

Item URL in elib:https://elib.dlr.de/78478/
Document Type:Article
Title:Water ice abundance and CO2 band strength on the saturnian satellite Phoebe from Cassini/VIMS observations
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Hansen, G. B. University of Washington, Seattle, USA.UNSPECIFIEDUNSPECIFIED
Hollenbeck, E.C.University of Washington, Seattle, USA.UNSPECIFIEDUNSPECIFIED
Apple, S.K.University of Washington, Seattle, USA.UNSPECIFIEDUNSPECIFIED
Shin-White, E.-J., C.University of Washington, Seattle, USA.UNSPECIFIEDUNSPECIFIED
Date:August 2012
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 331-338
Keywords: Saturn, Satellites; Satellites, Composition; Satellites, Surfaces; Spectroscopy; Ices, IR spectroscopy
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
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:21 Nov 2012 08:00
Last Modified:20 Mar 2013 19:45

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