Spectra of the Wells lunar glass simulants: New old data for reflectance modeling

Silicate glasses are an important constituent in the regolith of airless planetary bodies, and knowledge of glass reflectance characteristics is important for remote‐sensing studies of the Moon, Mercury, and asteroids. We recovered reflectance spectra for 20 vacuum‐melted lunar glass simulants measured by Wells (1977), which cover a wider range of Fe and Ti contents (0–17.5 wt % FeO and 0–15 wt % TiO2) and a wider wavelength range than those of the better‐known Bell et al. (1976) study. We examine the spectra in terms of known absorptions, explore the relationship between ultraviolet spectral parameters and composition, and apply the Hapke radiative transfer model to predict the reflectance spectra of the Wells glasses. The imaginary part of the refractive index (k) at each wavelength was computed based on the Ti and Fe composition using the linear relationship presented by Wilcox et al. (2006) and with a new linear‐exponential hybrid relationship. Comparison of the model spectra with the measured spectra reveals that the samples rich in Fe and Ti are best modeled by the linear relationship, because the linear model was developed using the Fe‐ and/or Ti‐rich Bell et al. (1976) glasses. For Fe‐ and Ti‐poor glasses, the hybrid model provides a better fit to the measured spectra, because this model for k is based on the wider compositional range of the Wells glasses. In the future, better linear model fits might be obtained if optical parameters were derived for a wider compositional range, from low‐Fe/low‐Ti to the higher‐Fe/higher‐Ti compositions of Apollo volcanic glasses.

[1]  T. McCord,et al.  Application of Remote Spectral Reflectance Measurements to Lunar Geology Classification and Determination of Titanium Content of Lunar Soils , 1974 .

[2]  H. Mao,et al.  Optical spectra and electron paramagnetic resonance of lunar and synthetic glasses: a study of the effects of controlled atmosphere, composition, and temperature. , 1976 .

[3]  E. Wells.  Optical Absorption Bands in Glasses of Lunar Composition. , 1977 .

[4]  B. Hapke,et al.  Lunar Soil: Iron and Titanium Bands in the Glass Fraction , 1977, Science.

[5]  J. J. Moré,et al.  Levenberg--Marquardt algorithm: implementation and theory , 1977 .

[6]  R. Singer,et al.  Mars - Large scale mixing of bright and dark surface materials and implications for analysis of spectral reflectance , 1979 .

[7]  B. N. Church,et al.  Calculation of the refractive index of silicate glasses from chemical composition , 1980 .

[8]  B. Hapke.  Bidirectional reflectance spectroscopy: 1. Theory , 1981 .

[9]  B. Hapke,et al.  Bidirectional reflectance spectroscopy: 2. Experiments and observations , 1981 .

[10]  Carle M. Pieters,et al.  Moon: near-infrared spectral reflectance, a first good look. , 1981 .

[11]  K. Housen,et al.  REGOLITHS ON SMALL BODIES IN THE SOLAR SYSTEM , 1982 .

[12]  E. M. Shoemaker,et al.  Large Body Impacts Through Geologic Time , 1984 .

[13]  Lisa R. Gaddis,et al.  Remote sensing of lunar pyroclastic mantling deposits , 1985 .

[14]  W. M. Cady,et al.  Patterns of change in earth evolution , 1986 .

[15]  J. Delano.  Pristine lunar glasses: Criteria, data, and implications , 1986 .

[16]  R. Greenberg,et al.  Asteroidal regoliths: what we do not know , 1989 .

[17]  Jeffrey R. Johnson,et al.  A reevaluation of spectral ratios for Lunar Mare TiO2 mapping , 1991 .

[18]  Mark J. Cintala,et al.  Impact‐induced thermal effects in the lunar and Mercurian regoliths , 1992 .

[19]  Carle M. Pieters,et al.  Estimating modal abundances from the spectra of natural and laboratory pyroxene mixtures using the modified Gaussian model , 1993 .

[20]  J. Mustard,et al.  Effects of Hyperfine Particles on Reflectance Spectra from 0.3 to 25 μm , 1997 .

[21]  Paul G. Lucey,et al.  Mapping the FeO and TiO2 content of the lunar surface with multispectral imagery , 1998 .

[22]  Paul G. Lucey,et al.  Model near‐infrared optical constants of olivine and pyroxene as a function of iron content , 1998 .

[23]  Gorachand Ghosh,et al.  Handbook of thermo-optic coefficients of optical materials with applications , 1998 .

[24]  Paul G. Lucey,et al.  Lunar iron and titanium abundance algorithms based on final processing of Clementine ultraviolet‐visible images , 2000 .

[25]  R. Morris,et al.  Lunar Mare Soils: Space weathering and the major effects of surface‐correlated nanophase Fe , 2001 .

[26]  Lisa R. Gaddis,et al.  Compositional analyses of lunar pyroclastic deposits , 2003 .

[27]  Paul G. Lucey,et al.  Radiative transfer modeling of compositions of lunar pyroclastic deposits , 2006 .

[28]  Matthew E. Pritchard,et al.  Thermal and Magmatic Evolution of the Moon , 2006 .

[29]  Bruce A. Campbell,et al.  Understanding the Lunar Surface and Space-Moon Interactions , 2006 .

[30]  P. Lucey,et al.  Radiative transfer modeling of lunar highlands spectral classes and relationship to lunar samples , 2007 .

[31]  P. Lucey,et al.  Near‐infrared optical constants of pyroxene as a function of iron and calcium content , 2007 .

[32]  P. Lucey,et al.  Radiative transfer mixing models of meteoritic assemblages , 2007 .

[33]  S. Murchie,et al.  Spectroscopic Observations of Mercury's Surface Reflectance During MESSENGER's First Mercury Flyby , 2008, Science.

[34]  S. Murchie,et al.  Explosive volcanic eruptions on Mercury: Eruption conditions, magma volatile content, and implications for interior volatile abundances , 2008 .

[35]  Craig B. Markwardt,et al.  Non-linear Least Squares Fitting in IDL with MPFIT , 2009, 0902.2850.

[36]  Carle M. Pieters,et al.  Spectral characteristics of lunar impact melts and inferred mineralogy , 2010 .

[37]  Richard D. Starr,et al.  The Major-Element Composition of Mercury’s Surface from MESSENGER X-ray Spectrometry , 2011, Science.

[38]  S. Murchie,et al.  The global distribution of pyroclastic deposits on Mercury: the view from MESSENGER flybys 1-3. , 2011 .

[39]  Richard D. Starr,et al.  Major-Element Abundances on the Surface of Mercury: Results from the MESSENGER Gamma-Ray Spectrometer , 2012 .

[40]  Sean C. Solomon,et al.  Chemical heterogeneity on Mercury's surface revealed by the MESSENGER X-Ray Spectrometer , 2012 .

[41]  T. Roush,et al.  Retrieving Optical Constants of Glasses with Variable Iron Abundance , 2013 .

[42]  William E. McClintock,et al.  The low-iron, reduced surface of Mercury as seen in spectral reflectance by MESSENGER , 2014 .

[43]  David E. Smith,et al.  Global inventory and characterization of pyroclastic deposits on Mercury: New insights into pyroclastic activity from MESSENGER orbital data , 2014 .