Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

Hapke, Bruce; Wells, Edward F.; Wagner, J. K.; Partlow, W. D.

doi:10.1016/0019-1035(81)90184-6

Cited by 54 publications

(41 citation statements)

References 10 publications

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“…In the 1400−1800 Å wavelength region, a slight blue slope would be expected if water ice existed on the surface, due to a broad water ice absorption band centered around 1600 Å in the FUV. However, if water ice were detected with Alice, at the longer wavelengths beyond 1800 Å, outside of the absorption band, we should see a rise in the bidirectional reflectance of 67P (Hapke et al 1981;Wagner et al 1987;Hendrix & Hansen 2008), which we do not. In fact, the spectra presented here do not show indications of any absorption features or absorption edges.…”

Section: Discussioncontrasting

confidence: 56%

“…This is considered to be blue sloped because of the decrease with increasing wavelength and is consistent with the derived values of the single scattering albedo, w, which also decreases from 1425−1525 Å to 1700−1800 Å (Table 3). While a blue slope may be suggestive of water ice on the surface in this finite FUV region as seen in the laboratory (Hapke et al 1981;Wagner et al 1987), using Hapke modeling as in Hendrix & Hansen (2008) it has also been shown that the water ice spectrum is expected to have a red slope at these wavelengths due to the location of the edge of the FUV cut-off if water ice were present. Therefore, the FUV blue slope alone is inconclusive with respect to the presence of water ice.…”

Section: Photometric Correctionmentioning

confidence: 84%

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Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

Feaga

Protopapa

Schindhelm

et al. 2015

A&A

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Aims. The Alice far-ultraviolet (FUV) spectrograph onboard Rosetta has, for the first time, imaged the surface of a comet, 67P/Churyumov-Gerasimenko (67P), in the FUV. With spatially resolved data, the nucleus properties are characterized in the FUV, including phase dependence, albedo, and spectral slope. Regional measurements across the nucleus are compared to discern any compositional variations. Methods. Hapke theory was utilized to model the phase dependence of the material on the surface of 67P. The phase dependence of 67P was derived from a subset of data acquired at various phase angles in November 2014, within 50 km of the comet such that the nucleus was spatially resolved. The derived photometric correction was then applied to a different subset of spatially resolved data sampling several distinct geographical regions on the nucleus acquired in August−November 2014 under similar viewing geometries. Results. In the FUV, the surface of 67P is dark, blue sloped, has an average geometric albedo of 0.054 ± 0.008 at 1475 Å near the center of the Alice bandpass, and is mostly uniform from region to region, with the exception of the Hatmehit region, which is slightly more reflective. These results are consistent with the suggestion made by the Rosetta OSIRIS and VIRTIS teams that the surface of 67P is covered with a homogeneous layer of material and that surface ice is not ubiquitous in large abundances. The modeled Hapke parameters, specifically the single scattering albedo (w) and the asymmetry factor (ζ), are determined to be 0.031 ± 0.003 and −0.530 ± 0.025 near the center of the Alice bandpass at 1475 Å. These parameters are consistent with measurements of other comet nuclei that have been observed by flyby missions in the visible and the near-infrared regimes.

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Section: Discussioncontrasting

confidence: 56%

Section: Photometric Correctionmentioning

confidence: 84%

Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

Feaga

Protopapa

Schindhelm

et al. 2015

A&A

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“…However, if so, we can exclude pure frosts of H 2 O, CO 2 , NH 3 ,and SO 2 . The reflectance measured for each of these pure ices is flat in the optical and slightly rising to its peak at ≈0.2 μm (except SO 2 ,which remains flat) before each drops rapidly to its minimum reflectance at ≈0.16 μm (Hapke et al 1981). These same disk models were then used to construct a synthetic image, discussed in Section 4.3.…”

Section: Grain Propertiesmentioning

confidence: 99%

Panchromatic Imaging of a Transitional Disk: The Disk of Gm Aur in Optical and Fuv Scattered Light

Hornbeck

Swearingen

Grady

et al. 2016

ApJ

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We have imaged GMAurigae with the Hubble Space Telescope, detected its disk in scattered light at 1400 and 1650 Å, and compared these with observations at 3300 Å, 5550 Å, 1.1 μm, and 1.6 μm. The scattered light increases at shorter wavelengths. The radial surface brightness profile at 3300 Å shows no evidence of the 24 au radius cavity that has been previously observed in submillimeter observations. Comparison with dust grain opacity models indicates thatthe surface of the entire disk is populated with submicron grains. We have compiled aspectral energy distribution from 0.1 μm to 1mmand used it to constrain a model of the star+disk system that includes the submillimeter cavity using the Monte Carlo radiative transfer code by Barbara Whitney. The best-fit model image indicates that the cavity should be detectable in the F330W bandpass if the cavity has been cleared of both large and small dust grains, but we do not detect it. The lack of an observed cavity can be explained by the presence of submicron grains interior to the submillimeter cavity wall. We suggest one explanation for this thatcould be due to a planet of mass <9 M J interior to 24 au. A unique cylindrical structure is detected in the far-UV data from the Advanced Camera for Surveys/Solar Blind Channel. It is aligned along the system semiminor axis, but does not resemble an accretion-driven jet. The structure is limbbrightened and extends 190±35 au above the disk midplane. The inner radius of the limbbrightening is 40±10 au, just beyond the submillimeter cavity wall.

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“…With our spectral resolution, we can not distinguish between the various possibilities of SO 2 or sulfur (Ockert et al 1987, Lane et al 1981, Fanale et al 1999, O 3 (Noll et al 1997), or any of a number of abundant ices which have steep absorption edges in the UV between 320 (SO 2 ), and 230 nm (NH 3 , H 2 O) (Hapke et al 1981). We also note that Jenniskens (1993) shows that the absorptivity of several organic refractory residues continues to increase dramatically between 300 and 100 nm, but in a fairly smooth fashion except for one sample that is actually more absorbing in the 336-nm region than at shorter wavelengths.…”

Section: Compositional Variations Within the Ringsmentioning

confidence: 99%

HST Multicolor (255–1042 nm) Photometry of Saturn's Main Rings I: Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra

Cuzzi

French

Dones

2002

Icarus

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as the ring opening angle to Earth and Sun increased from 4• to 24• , with a spread of phase angles between 0.3• and 6• at each opening angle. The rings were routinely observed in the five HST wideband UBVRI filters (F336W, F439W, F555W, F675W, and F814W) and occasionally in the F255W, F785LP, and F1042M filters. The emphasis in this series of papers will be on radial color (implying compositional) variations. In this first paper we describe the analysis technique and calibration procedure, note revisions in a previously published Voyager ring color data analysis, and present new results based on over 100 HST images.In the 300-600 nm spectral range where the rings are red, the 555/336-nm ratio increases by about 14% as the phase angle increases from 0.3• to 6• . This effect, never reported previously for the rings, is significantly larger than the phase reddening which characterizes other icy objects, primarily because of the redness of the rings. However, there is no discernible tendency for color to vary with ring opening angle at a given phase angle, and there is no phase variation of color where the spectrum is flat. We infer from this combination of facts that multiple intraparticle scattering, either in a regolith or between facts of an unusually rough surface, is important in these geometries, but that multiple interparticle scattering in a vertically extended layer is not. Voyager color ratios at a phase angle of 14• are compatible with this trend, but calibration uncertainties prevent their use in quantitative modeling.Overall ring average spectra are compatible with those of earlier work within calibration uncertainties, but ring spectra vary noticeably with region. We refine and subdivide the regions previously defined by others. The variation seen between radial profiles of ratios between different wavelengths suggests the presence of multiple compositional components with different radial distributions. We present new radial profiles of far-UV color ratio (F336W/F255W) showing substantial global variations having a different radial structure than seen between 555 and 336 nm. We constrain radial variation in the strength of a putative 850-nm spectral feature to be at the percent level or less. There seem to be real variations in the shape of regional ring spectra between 800 and 1000 nm. c 2002 Elsevier Science (USA)

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Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

Cited by 54 publications

References 10 publications

Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

Panchromatic Imaging of a Transitional Disk: The Disk of Gm Aur in Optical and Fuv Scattered Light

HST Multicolor (255–1042 nm) Photometry of Saturn's Main Rings I: Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra

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