Radiative transfer modeling of near‐infrared spectra of lunar mare soils: Theory and measurement

Abstract

[1] We examine the ability of a radiative transfer model based on the theory of Hapke (1981, 1993, 2001) to reproduce reflectance spectra of known composition, as well as extract compositional information from reflectance spectra. We test this model using spectra of two-component mineral mixtures, spectra of lunar mare soils studied by the Lunar Soil Characterization Consortium (LSCC), and a telescopic spectrum of the Apollo 11 landing site. The model is able to accurately reproduce spectra of two-component mineral mixtures and can be used to accurately predict mineral abundances, mineral chemistry, and particle size. Reflectance spectra of the lunar mare soils are modeled using the mineral abundances and chemistries reported for each soil. We collect our own mineral and chemical information for one of these samples, 12001, in order to examine the effects of several simplifying assumptions employed by the LSCC and conclude that the classification of glass (volcanic/impact versus agglutinitic) can have large consequences on the predicted spectra. Model spectra can generally mimic the lunar mare sample spectra, though with consistent errors in contrast and continuum slope, and absorption bands offset to shorter wavelengths. The Apollo 11 telescopic spectrum is successfully modeled with mineralogy and chemistry from sample 10084, though the fit is improved with slight variations in mineralogy or mineral chemistry. We find that varying pyroxene chemistry can have as large an effect on spectral shape as varying mineral abundance.

Asteroid Photometry

“…Forward-modeling of remotely-sensed reflectance spectra with Hapke theory has been routinely accomplished for many years for a wide range of planetary objects (cf. Roush et al, 1990;Calvin and Clark, 1991;Lucey, 1998;Verbiscer et al, 2006;Wilcox et al, 2006;Denevi et al, 2008;Warell and Davidsson, 2010). The model successfully predicts the scattering behavior of idealized soil samples (Hapke et al, 2009;Hapke and Wells, 1981;Hapke, 2012b).…”

Quantitative compositional analysis of martian mafic regions using the MEx/OMEGA reflectance data 1. Methodology, uncertainties and examples of application

“…Employing such a theory in concert with optical constants of components allows computational exploration of the extensive space of parameters. A widely accepted theoretical model describing such scattering has been developed by Hapke (1981) and has been used to analyze the surface properties of the Moon, asteroids and satellites (e.g., Johnson and Grundy, 2001;Cruikshank et al, 2003Cruikshank et al, , 2005Denevi et al, 2008). Recently, other models (Douté and Schmitt, 1998;Shkuratov et al, 1999) have started to play an important role, which gives the opportunity to extend the analysis of OMEGA spectra beyond the simple recognition of mineral type, by quantifying their abundances.…”

Optical spectroscopic characterizations of laser irradiated olivine grains

“…Because the VNIR features below 2.5 µm in olivine and pyroxene spectra are mainly caused by electronic transitions of ferrous ions in crystal field (Burns 1993), the VNIR spectra may be greatly affected by the production of npFe 0 . The VNIR spectral effects of the npFe 0 with varying contents, distributions, and particle sizes have been studied by using the Hapke radiative transfer model with some success (e.g., Hapke 2001; Lawrence & Lucey 2007;Denevi et al 2008). In contrast, space weathering effects on reflectance bands at longer wavelengths caused by thermal lattice vibrations are less well studied, but may contain rich information on space weathered minerals (Lucey et al 2016).…”