Brown, R.H.

Buratti, B.J.

Capaccioni, F.

Cerroni, P.

Ciarniello, Mauro

Clark, R. N.

Coradini, A.

Cruikshank, D.P.

Filacchione, G.

Stephan, K.

Tosi, F.

English

Institute of Transport Research:Publications

2010 AGU Fall Meeting�You may print by clicking on this Print  button. To return to the previous page, close this browserwindow or click the 'X' button in the top right corner of the page.�ID# P33A-1558Location: Poster Hall (Moscone South)Time of Presentation: Dec 15 1:40 PM - 6:00 PM�Spectrophotometric Modeling of Enceladus Surface Properties and Composition from VimsDataM. Ciarniello1; F. Capaccioni1; G. Filacchione1; R. N. Clark3; D. P. Cruikshank4; P. Cerroni1; A.Coradini2; R. H. Brown5; B. J. Buratti6; F. Tosi2; K. Stephan71. INAF-IASF, Rome, Italy.2. INAF-IFSI, Rome, Italy.3. U.S. Geological Survey , Denver, CO, United States.4. NASA Ames Research Center, Moffett Field, CA, United States.5. Lunar and Planetary Lab and Steward Observatory, University of Arizona, Tucson, AZ, United States.6. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States.7. Institute for Planetary Exploration, DLR, Berlin, Germany.�The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft, is animaging spectrometer that produces monochromatic images in the 0.35 - 5.12 µm range. During the fiveyears of Cassini mission in the system of Saturn the instrument produced more than 1400 full-diskimages of the moons in a wide range of solar phase angles. This huge amount of data allows the study ofthe spectral and photometric surface properties of the Saturnian satellites. Our work started with theanalysis of Rhea’s surface properties (Ciarniello et al., submitted) and we now focus on Enceladus.We applied the Hapke’s radiative transfer model (Hapke,1993) to study the satellite’s spectrum at eachavailable phase angle and the phase curve at each wavelength in the VIMS range. This approach allowsto constrain physical properties of the medium composing the surface such as grain size, amount ofcontaminants, opposition effect mechanisms and surface roughness.The 1.5, 2.0 and 3.0 µm absorption bands in the spectrum indicate that the surface of the moon is mainlycomposed of water ice. However the spectrum shows a small UV downturn which can be explained bythe presence of organic contaminants. In order to reproduce this behavior we modeled the surface usinga monodisperse grain size distribution of water ice with small inclusions of contaminants. Three mixingmodes have been investigated: areal, intimate and intraparticle. Four different organic contaminantshave been used: Triton tholin, Titan tholin, Hydrogenated amorphous carbon and tholin from Khare et al.1993. The best fit is obtained with an intraparticle mixture of water ice and a tiny amount of Triton tholin(0.001%) with particle radius between 60-70 µm.The spectral fit allows to decouple spectral effects by photometric ones and represents the starting pointfor the phase curve fit allowing to compute the single scattering albedo of the medium.The fit of phase curve for each wavelength shows a correlation between the parameters affecting itsshape (opposition effect amplitude and width, single particle phase function parameters and surfaceroughness slope) with the single scattering albedo.We compared the result of this work with our previous study performed on Rhea in order to point outcompositional similarities between the two moons.The approach we developed in this work is applicable to all the Saturn’s icy moons and represents apowerful tool to characterize their surface properties and to understand the processes that model them.Additionally, this method will allow to determine the distribution of organic compounds in the Saturniansystem and to study the surface evolution of the moons.This work is supported by an Italian Space Agency grant.Abstract�Central�-�Itinerary�abstract�details�popup http://agu-fm10.abstractcentral.com/planner?NEXT_PAGE=IT...1�of�2 12/21/10�15:36Contact InformationMauro Ciarniello, Roma, RM, Italy, 00133, click here to send an emailScholarOne Abstracts® (patent #7,257,767 and #7,263,655). © ScholarOne, Inc., 2010. All Rights Reserved.ScholarOne Abstracts and ScholarOne are registered trademarks of ScholarOne, Inc.Terms and Conditions of UseAbstract�Central�-�Itinerary�abstract�details�popup http://agu-fm10.abstractcentral.com/planner?NEXT_PAGE=IT...2�of�2 12/21/10�15:36

Spectrophotometric Modeling of Enceladus Surface Properties and Composition from Vims Data.

Spectrophotometric Modeling of Enceladus Surface Properties and Composition from Vims Data.

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