The surface composition of Iapetus: Mapping results from Cassini VIMS

Clark, R. N.; Cruikshank, D. P.; Jaumann, R.; Brown, R. H.; Stephan, K.; Ore, C. M. Dalle; Livo, Keith E.; Pearson, N.; Curchin, J. M.; Hoefen, Todd M.; Buratti, B. J.; Filacchione, G.; Baines, K. H.; Nicholson, P. D.

doi:10.1016/j.icarus.2012.01.008

Cited by 155 publications

(173 citation statements)

References 62 publications

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“…On the Saturnian satellites, most of the surface ice observed in the 1 to 5 μm spectral range is in the crystalline state, implying there is very little amorphous ice even on the very outside of grain surfaces (e.g., Clark et al, 2012;Newman et al, 2008;Scipioni et al, 2017 ). At Saturn, the active moon Enceladus is a source of the particles that make up the E ring, which coexists with the orbits of the inner satellites.…”

Section: Charged Particle Bombardment Of the Inner Saturnian Satellitesmentioning

confidence: 99%

Magnetospheric considerations for solar system ice state

Paranicas¹,

Hibbitts²,

Kollmann³

et al. 2018

Icarus

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a b s t r a c tThe current lattice configuration of the water ice on the surfaces of the inner satellites of Jupiter and Saturn is likely shaped by many factors. But laboratory experiments have found that energetic proton irradiation can cause a transition in the structure of pure water ice from crystalline to amorphous. It is not known to what extent this process is competitive with other processes in solar system contexts. For example, surface regions that are rich in water ice may be too warm for this effect to be important, even if the energetic proton bombardment rate is very high. In this paper, we make predictions, based on particle flux levels and other considerations, about where in the magnetospheres of Jupiter and Saturn the ∼MeV proton irradiation mechanism should be most relevant. Our results support the conclusions of Hansen and McCord (2004), who related relative level of radiation on the three outer Galilean satellites to the amorphous ice content within the top 1 mm of surface. We argue here that if magnetospheric effects are considered more carefully, the correlation is even more compelling. Crystalline ice is by far the dominant ice state detected on the inner Saturnian satellites and, as we show here, the flux of bombarding energetic protons onto these bodies is much smaller than at the inner Jovian satellites. Therefore, the ice on the Saturnian satellites also corroborates the correlation.

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Section: Charged Particle Bombardment Of the Inner Saturnian Satellitesmentioning

confidence: 99%

Magnetospheric considerations for solar system ice state

Paranicas¹,

Hibbitts²,

Kollmann³

et al. 2018

Icarus

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“…The reasons for this are enigmatic, but are perhaps due to the differences in surface compositions between topographic features, the proximity to bright material in each of the regions, and/or changes in spacecraft geometry between the three observations. we see that elemental sulfur does have a reflectance peak (emissivity minimum) near 855 cm −1 and even has another weaker feature at ∼660 cm −1 as in our CIRS spectrum (Clark et al 2007), but also has a distinct yellow color caused by an abrupt drop to near-zero reflectance below ∼0.5 μm, which VIMS has not observed in Iapetus' dark terrains (e.g., Clark et al 2012 (Clark 1999), but also have shortwave IR absorptions that VIMS has not observed on Iapetus.…”

Section: Spectral Feature Identification and Discussionmentioning

confidence: 49%

“…These worlds are composed of much more than just H 2 O ice, with tantalizing evidence from Cassini's Visual and Infrared Mapping Spectrometer (VIMS) for CO 2 , possible NH 3 and hydrous minerals, organics, and metallic and oxidized Fe on Saturn's icy moons (e.g., Clark et al 2005Clark et al , 2012. These non-H 2 O constituents appear to be concentrated in the darker terrains of Saturn's outer icy moons: Phoebe, Iapetus, Hyperion, Rhea, and Dione (Clark et al 2008;Stephan et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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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“…However, the suggested presence of NH 3 ·H 2 O along with Quaoar's size hints at the possibility that volcanism could occur on its surface, as has been described for volatile-rich objects (Stevenson 2004). Alternatively, crystalline H 2 O ice could be the product of impact gardening as proposed by Porter et al (2010) and NH 3 ·H 2 O could be seeping up to the surface of Quaoar by a diffusive mechanism, or its spectral signature could be influenced by the presence of sub-micron particles on the surface, as described by Clark et al (2012). A107, page 6 of 7…”

Section: Discussionmentioning

confidence: 81%

“…The addition of NH 3 ·H 2 O in the amounts shown in Table 3 brings the depth of the 2.0-μm band to fit the data. However, we should also note that some part of the discrepancy in depth between the two H 2 O bands could be caused by the contribution of sub-micron particles introducing a Rayleigh scattering component to the spectrum (Clark et al 2012). Such a component would be missing from our model as the adopted modeling code does not include a Rayleigh scattering module and might introduce the observed mismatch between the model and the observations.…”

Section: Modelling Of Spectral Datamentioning

confidence: 99%

(50000) Quaoar: Surface composition variability

Barucci

Ore

Perna

et al. 2015

A&A

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Aims. The goal of this work is to investigate the composition of the surface of (50000) Quaoar and its spatial variability. Methods. We present new continuous spectra from the visible to near-IR (0.3−2.3 μm) obtained with the X-Shooter instrument at the VLT-ESO at four different epochs on the surface of Quaoar. The data represent the highest spectral resolution data ever obtained for this object and the first near-IR dataset acquired in a single exposure over the entire wavelength range. They are complemented by previously published photometric observations obtained in the near-IR (3.6, 4.5 μm) with the Spitzer Space Telescope, which provide an extra set of constraints in the model calculation. Spectral modelling was performed for the entire wavelength range by means of a code based on the Shkuratov radiative transfer formulation and of an updated value of albedo obtained from recent Herschel observations. Results. We obtained compositional information for different observed areas that can cover about 40% of the assumed rotational period of 8.84 h. Our analysis helps to prove the presence of CH 4 and C 2 H 6 , as previously reported, along with indications of the possible presence of NH 3 ·H 2 O. New evidence of N 2 is inferred from the shift in the CH 4 bands. The albedo at the two Spitzer bands suggests there may be CO diluted in N 2 , and CO 2 for one of the surface locations. Conclusions. The spectral similarities indicate the overall homogeneity of the surface composition of one hemisphere of Quaoar, while some subtle variations are apparent when modelling. The presence of NH 3 ·H 2 O would support the idea that Quaoar's surface may be relatively young.

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The surface composition of Iapetus: Mapping results from Cassini VIMS

Cited by 155 publications

References 62 publications

Magnetospheric considerations for solar system ice state

Magnetospheric considerations for solar system ice state

Silicates on Iapetus From Cassini’s Composite Infrared Spectrometer

(50000) Quaoar: Surface composition variability

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