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Composition of Titan's Surface from Cassini VIMS

McCord, T.B. and Hansen, G.B. and Buratti, B.J. and Clark, R.N. and Cruikshank, D.P. and D'Aversa, E. and Griffith, C.A. and Baines, K.H. and Brown, R.H. and Dalle Ore, C.M. and Filacchione, G. and Formisano, V. and Hibbitts, C.A. and Jaumann, R. and Lunine, J.I. and Nelson, R.M. and Sotin, C. (2006) Composition of Titan's Surface from Cassini VIMS. Planetary and Space Science, 54 (15), pp. 1524-1539. Elsevier Ltd.. DOI: 10.1016/j.pss.2006.06.007

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Abstract

Titan's bulk density along with Solar System formation models indicates considerable water as well as silicates as its major constituents. This satellite's dense atmosphere of nitrogen with methane is unique. Deposits or even oceans of organic compounds have been suggested to exist on Titan's solid surface due to UV-induced photochemistry in the atmosphere. Thus, the composition of the surface is a major piece of evidence needed to determine Titan's history. However, studies of the surface are hindered by the thick, absorbing, hazy and in some places cloudy atmosphere. Ground-based telescope investigations of the integral disk of Titan attempted to observe the surface albedo in spectral windows between methane absorptions by calculating and removing the haze effects. Their results were reported to be consistent with water ice on the surface that is contaminated with a small amount of dark material, perhaps organic material like tholin. We analyze here the recent Cassini Mission's visual and infrared mapping spectrometer (VIMS) observations that resolve regions on Titan. VIMS is able to see surface features and shows that there are spectral and therefore likely compositional units. By several methods, spectral albedo estimates within methane absorption windows between 0.75 and 5 μm were obtained for different surface units using VIMS image cubes from the Cassini-Huygens Titan T<sub>a</sub> encounter. Of the spots studied, there appears to be two compositional classes present that are associated with the lower albedo and the higher albedo materials, with some variety among the brighter regions. These were compared with spectra of several different candidate materials. Our results show that the spectrum of water ice contaminated with a darker material matches the reflectance of the lower albedo Titan regions if the spectral slope from 2.71 to 2.79 μm in the poorly understood 2.8-μm methane window is ignored. The spectra for brighter regions are not matched by the spectrum of water ice or unoxidized tholin, in pure form or in mixtures with sufficient ice or tholin present to allow the water ice or tholin spectral features to be discerned. We find that the 2.8-μm methane absorption window is complex and seems to consist of two weak subwindows at 2.7 and 2.8 μm that have unknown opacities. A ratio image at these two wavelengths reveals an anomalous region on Titan that has a reflectance unlike any material so far identified, but it is unclear how much the reflectances in these two subwindows pertain to the surface.

Item URL in elib:https://elib.dlr.de/50434/
Document Type:Article
Title:Composition of Titan's Surface from Cassini VIMS
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
McCord, T.B.Space Science Inst., Wintrop WAUNSPECIFIED
Hansen, G.B.Dept. of E & Sp. Sci., U. of Washington, Seattle WA, USAUNSPECIFIED
Buratti, B.J.Jet Prop. Lab., Pasadena, USAUNSPECIFIED
Clark, R.N.USGS, Denver Federal Center, Denver CO, USAUNSPECIFIED
Cruikshank, D.P.NASA Ames Res. Center, Astrophysics Branch, Moffett Field, CA, USAUNSPECIFIED
D'Aversa, E.Istituto Fisica Spazio Interplanetario, CNR, Roma, ItalyUNSPECIFIED
Griffith, C.A.Dept. Pl. Sci. and LPL, U. of AZ, Tucson AZUNSPECIFIED
Baines, K.H.Jet Prop. Lab., Pasadena CA, USAUNSPECIFIED
Brown, R.H.Dept. Pl. Sci. and LPL, U. of AZ, Tucson AZUNSPECIFIED
Dalle Ore, C.M.NASA Ames Res. Center, Astrophysics Branch, Moffett Field, CA, USA; SETI Inst., Mountain View, CA, USAUNSPECIFIED
Filacchione, G.Istituto Fisica Spazio Interplanetario, CNR, Roma, ItalyUNSPECIFIED
Formisano, V.Istituto Fisica Spazio Interplanetario, CNR, Roma, ItalyUNSPECIFIED
Hibbitts, C.A.Johns Hopkins U. Appl. Phys. Lab., Columbia MD, USAUNSPECIFIED
Jaumann, R.UNSPECIFIEDUNSPECIFIED
Lunine, J.I.Istituto Fisica Spazio Interplanetario, CNR, Roma, Italy; Dept. Pl. Sci and LPL, U. of AZ, Tucson AZUNSPECIFIED
Nelson, R.M.Jet Prop. Lab. Pasadena CA, USAUNSPECIFIED
Sotin, C.Univ. of Nantes Cedex, France and the Cassini VIMS TeamUNSPECIFIED
Date:December 2006
Journal or Publication Title:Planetary and Space Science
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:Yes
Volume:54
DOI :10.1016/j.pss.2006.06.007
Page Range:pp. 1524-1539
Publisher:Elsevier Ltd.
Status:Published
Keywords:Saturnian system, Titan, Surface composition, Cassini, VIMS
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EW - Erforschung des Weltraums
DLR - Research area:Space
DLR - Program:W EW - Erforschung des Weltraums
DLR - Research theme (Project):W - Vorhaben CASSINI (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Geology
Deposited By: Vogt, Irene
Deposited On:22 Aug 2007
Last Modified:22 Feb 2010 15:49

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