Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system

Clark, R. N.; Curchin, J. M.; Jaumann, R.; Cruikshank, D. P.; Brown, R. H.; Hoefen, Todd M.; Stephan, K.; Moore, Jeffrey M.; Buratti, B. J.; Baines, K. H.; Nicholson, P. D.; Nelson, Robert M.

doi:10.1016/j.icarus.2007.08.035

Cited by 143 publications

(142 citation statements)

References 34 publications

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“…However, Clark et al (2008Clark et al ( , 2011b, showed that the visible colors and UV absorber are consistent with a single source with varying abundance of the contaminants. Key to solution of the problem was the discovery of Rayleigh scattering from small particles (Clark et al, 2008). From the VIMS data the spectral behaviour in the VIS-NIR range shows similarities between Iapetus and Hyperion; while the IR spectra point out a strong correlation between the features observed on Iapetus and Phoebe.…”

Section: Introduction and Rationalementioning

confidence: 94%

“…The origin of the material that causes the albedo dichotomy of Iapetus has been the subject of a long standing debate (Buratti and Hicks, 2003;Spencer and Denk, 2010;Tosi et al, 2010). However, Clark et al (2008Clark et al ( , 2011b, showed that the visible colors and UV absorber are consistent with a single source with varying abundance of the contaminants. Key to solution of the problem was the discovery of Rayleigh scattering from small particles (Clark et al, 2008).…”

Section: Introduction and Rationalementioning

confidence: 99%

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Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Ciarniello

Capaccioni

Filacchione

et al. 2011

Icarus

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The surface properties of the icy bodies in the saturnian system have been investigated by means of the CASSINI-VIMS (Visual Infrared Mapping Spectrometer) hyperspectral imager which operates in the 0.35-5.1 m wavelength range. In particular, we have analyzed 111 full disk hyperspectral images of Rhea ranging in solar phase between 0.08° and 109.8°. These data have been previously analyzed by Filacchione et al. (2007Filacchione et al. ( , 2010 to study, adopting various "spectral indicators" (such as spectral slopes, band depth, continuum level, etc.), the relations among various saturnian satellites.As a further step we proceed in this paper to a quantitative evaluation of the physical parameters determining the spectrophotometric properties of Rhea's surface. To do this we have applied Hapke (1993) IMSA model (Isotropic Multiple Scattering Approximation) which allow us to model the phase function at VIS-IR (visible-infrared) wavelengths as well as the spectra taking into account various types of mixtures of surface materials. Thanks to this method we have been able to constrain the size of water ice particles covering the surface, the amount of organic contaminants, the large scale surface roughness and the opposition effect surge. From our analysis it appears that wavelength dependent parameters, e.g. opposition surge width (h) and single-particle phase function parameters (b,v), are strongly correlated to the estimated single-scattering albedo of particles. For Rhea the best fit solution is obtained by assuming:1) an intraparticle mixture of crystalline water ice and a small amount (0.4%) of Triton tholin; 2) a monodisperse grain size distribution having a particle diameter a m = 38 µm; and 3) a surface roughness parameter value of 33°. The study of phase function shows that both Shadow Hiding and Coherent Backscattering contribute to the opposition surge. This study represents the first attempt, in the case of Rhea, to join the spectral and the photometric analysis. The surface model we derived gives a good quantitative description of both spectrum and phase curve of the satellite. The same approach and model, with appropriate modifications, shall be applied to VIMS data of the other icy satellites of Saturn, in order to reveal similarities and differences in the surface characteristics to understand how these bodies interact with their environment.

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Section: Introduction and Rationalementioning

confidence: 94%

Section: Introduction and Rationalementioning

confidence: 99%

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Ciarniello

Capaccioni

Filacchione

et al. 2011

Icarus

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“…Similar ice "contaminants" have been found on Hyperion (Tosi et al 2010;Dalton et al 2012), consistent with a common source of surface material for Saturn's three mid-sized moons orbiting beyond Titan. The later discovery of similar dark material on Dione and its spatial distribution there supported a hypothesis that this material arrived at all of these satellites from a source outside the Saturnian system (Clark et al 2008;Stephan et al 2010), while the discovery of the Phoebe ring in 2009 led to conclusions that dark particles were transported to Iapetus and Hyperion from Phoebe (Tosi et al 2010).…”

Section: Introductionmentioning

confidence: 87%

Silicates on Iapetus From Cassini’s Composite Infrared Spectrometer

Young

Wray

Clark

et al. 2015

ApJ

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We present the first spectral features obtained from Cassini's Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal-to-noise ratios (S/Ns) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/N and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ∼855 cm −1 and a possible doublet at 660 and 690 cm −1 that do not correspond to any known instrument artifacts. We attribute the 855 cm −1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm −1. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125 K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm −1 and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.

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“…Using this method, the primary surface component of the Saturnian satellites has been found to be water ice (e.g., McCord et al 1971;Fink et al 1976;Morrison et al 1976;Cruikshank 1980;Clark et al 1984), possibly in mixtures with other constituents (e.g., Emery et al 2005;Verbiscer et al 2006;Clark et al 2008). Most of the published spectral data of Enceladus focus on the near-IR: the Emery et al (2005) and Cruikshank et al (2005) spectra extend as short as 800 nm, as do the Verbiscer et al (2006) Enceladus spectra.…”

Section: Introductionmentioning

confidence: 99%

The surface composition of Enceladus: clues from the Ultraviolet

Hendrix

Hansen

2009

Proc. IAU

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Abstract. The reflectance of Saturn's moon Enceladus has been measured at far ultraviolet (FUV) wavelengths (115-190 nm) by Cassini's UltraViolet Imaging Spectrograph (UVIS). At visible and near infrared (VNIR) wavelengths Enceladus' reflectance spectrum is very bright, consistent with a surface composed primarily of H2 O ice. At FUV wavelengths, however, Enceladus is surprisingly dark -darker than would be expected for pure water ice. We find that the low FUV reflectance of Enceladus can be explained by the presence of a small amount of NH3 and a small amount of a tholin in addition to H2 O ice on the surface.

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Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system

Cited by 143 publications

References 34 publications

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Silicates on Iapetus From Cassini’s Composite Infrared Spectrometer

The surface composition of Enceladus: clues from the Ultraviolet

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