Near‐infrared optical constants of naturally occurring olivine and synthetic pyroxene as a function of mineral composition

Abstract

[1] Radiative transfer theory will assist in determining olivine and pyroxene proportions and compositions from the surface of a planetary body composed of intimately mixed minerals. In order to use radiative transfer techniques, the model requires the optical constants of olivine and pyroxene. Optical constants are parameters that describe the degree light absorbed (k) and refracted (n) in a medium. Here we only parameterize k in the near infrared from 0.6 to 2.5 mm of natural olivine as a function of forsterite number and synthetic pyroxene with respect to wollastonite and ferrosilite number. In contrast to previous work, this study is an improvement on previous work because we have a diverse and larger sample size leading to robust optical parameters. Additionally, we characterize each k-spectrum with the modified Gaussian model (MGM). MGM is a physically realistic model of near-infrared absorptions due to electronic transitions. In each spectrum, we model each absorption and continuum with Gaussians and an inverse of a linear function, respectively. We find that our fitting routine characterizes the olivine and pyroxene k-spectra in a robust and consistent manner. Then we use regression analysis to characterize each parameter of the Gaussians and the continuum as a function of mineral composition. The developed optical parameters from this work will allow calculations of mineral proportions and compositions on planetary surfaces with use of data from missions such as Dawn, MESSENGER, SELENE, and Chandrayaan-1.

Olivine‐Carbonate Mineralogy of the Jezero Crater Region

“…Library (Clark et al, 2007). In addition, we supplemented this collection of 11 USGS olivines with two additional USGS provided olivine spectra and eight additional olivines sourced from the RELAB reflectance database (http://www.planetary.brown.edu/relab/), in order to avoid biases due to reflectance measurements in a particular lab, as suggested by Trang et al (2013).…”

Surveying the South Pole-Aitken basin magnetic anomaly for remnant impactor metallic iron

“…To demonstrate how spectral reflectance varies with metallic iron abundance we performed a test with radiative transfer theory (Hapke, 1993(Hapke, , 2001(Hapke, , 2012Lucey and Riner, 2011) using the optical constants of orthopyroxene (Trang et al, 2013), metallic iron (Cahill et al, 2012), and plagioclase (Lucey, 2002), respectively. The spectrum of a noritic anorthosite assemblage (75 vol.% plagioclase; 25 vol.% orthopyroxene; Mg' of 75) was modeled and then the assemblage was modified in two ways.…”

Ilmenite mapping of the lunar regolith over Mare Australe and Mare Ingenii regions: An optimized multisource approach based on Hapke radiative transfer theory

“…Optical constants from Trang et al . [] should be tested to see if they can improve the correlation between the modeled and the true abundance of olivine and the pyroxenes. Table shows the ilmenite abundance of the 15 lunar soil samples used in our validation, as determined by the LSCC, and the maximum stoichiometrically possible ilmenite content calculated compared to our four different implementations of our radiative transfer modeling.…”

“…Recent optical constants for olivine and the pyroxenes (e.g., from Trang et al . []) could be used in the future to see if it the spectral fit can be improved, and if the correlation between the modeled and the true abundance of these minerals can be improved.…”

“…Optical constants from Trang et al . [] should be tested to see if they can improve the spectral fit between the modeled and the LSCC spectra, as well as if they can improve the correlation between the modeled and the true abundance of olivine and the pyroxenes.…”