Spectroscopy of Icy Moon Surface Materials

Low temperature optical constants of some hydrated sulfates relevant to planetary surfaces

“…For further discussion, see Roush et al [2007]. A search of the literature found no published transmission or specular reflection spectra of these materials over the full spectral range used here to set a robust upper limit on k [ Dalton , 2010]. Comparing to gypsum k at λ = 2.5 μ m from Roush et al [2007], we estimate that the bulk k peaks in regions of highest absorption could be up to 1.5–2 times higher.…”

“…To constrain surface composition on Jovian, Saturnian, and Uranian satellites, several groups have acquired laboratory spectra of ices and volatiles that may be compared to visible to near‐infrared (VNIR) spacecraft imaging and spectrometer data [ Fink and Sill , 1982; Khare et al , 1990; Bernstein et al , 2005, 2006, and references therein; Gerakines et al , 2000, 2005; Dalton et al , 2005; Mastrapa et al , 2008; Clark et al , 2009]. Dalton [2010]summarized published infrared spectra for ∼125 compounds that have been predicted to occur on icy bodies through past laboratory, numerical, and observational studies of comets, asteroids, icy moons, and interstellar molecular clouds. Recently published low‐temperature reflectance spectra for ten alkanes (methane through decane) and related hydrocarbons [ Clark et al , 2009] enable linear (area‐based) models to use the full wavelength range of Galileo and Cassini VNIR spectrometers.…”

“…Recently published low‐temperature reflectance spectra for ten alkanes (methane through decane) and related hydrocarbons [ Clark et al , 2009] enable linear (area‐based) models to use the full wavelength range of Galileo and Cassini VNIR spectrometers. Of the 125 compounds summarized by Dalton [2010], only four compounds (H 2 O, NH 3 , CH 4 , and CO 2 ) [ Warren , 1984; Martonchik et al , 1984; Hudgins et al , 1993; Hansen , 1997, 2005; Grundy and Schmitt , 1998; Grundy et al , 2002; Mastrapa and Brown , 2006; Mastrapa et al , 2008, 2009] have been sufficiently characterized across the appropriate temperatures, wavelengths, spectral resolutions, and sample thicknesses to permit quantitative abundance modeling of spacecraft observations by the Galileo Near Infrared Mapping Spectrometer (NIMS) [ Carlson et al , 1992], Cassini Visual and Infrared Mapping Spectrometer (VIMS) [ Brown et al , 2004], and New Horizons Linear Etalon Imaging Spectral Array (LEISA) [ Weaver et al , 2008]. Availability of laboratory reflectance spectra for these materials allows linear mixture modeling of spacecraft observations, constrains surface abundances to first order and informs models of surface and interior chemical evolution.…”

“…At the low surface temperatures of icy satellites, the infrared spectra of hydrated compounds vary significantly from their behavior at Earth room temperature (∼297–300 K) [ Dalton et al , 2005, and references therein]. Cryogenic data on three hydrated Mg sulfates, epsomite (MgSO 4 ·7H 2 O), bloedite (Na 2 Mg(SO 4 ) 2 ·4H 2 O), and hexahydrite (MgSO 4 ·6H 2 O), are highly sought [ Dalton , 2010, and references therein]. All three hydrates presented here have been proposed as surface constituents on Europa [ Clark and McCord , 1980; McCord et al , 1998, 1999a, 1999b, 2001, 2002; Dalton and Clark , 1999; Dalton , 2000, 2003].…”

Compositional analysis of Hyperion with the Cassini Visual and Infrared Mapping Spectrometer

“…The nominal spectral sampling is 16.6 nm from 0.85 to 5.10 lm (Brown et al, 2004;Dalton, 2010), with k/Dk = 255, sufficient to resolve major features of water ice, carbon dioxide, and organic materials. The VIMS-Visible portion of the instrument was not utilized in this study and so we will not discuss it here.…”