Visible and Near-Infrared (VNIR) reflectance spectroscopy of glassy igneous material: Spectral variation, retrieving optical constants and particle sizes by Hapke model
Journal
Date Issued
2016
Author(s)
Description
Rocks samples were kindly provided by Prof. M. Massironi
(University of Padova) and Prof. O. Zeda (University of Parma).
Glassy samples were produced at Volcanologist Laboratory with
the help of Dr. A. Vona (RomaTre University). Authors thank Dr.
D. Bersani and Dr. G. Serventi (University of Parma) for Brewster
angles measurements.
XRF analyses and density measurements were performed at
Geoscience Department, and Mössbauer data were collected at Biophysics
and Medical Physics Unit, Department of Neuroscience,
University of Parma. Reflectance spectra were carried out at Spectrocopic
LABoratory at IAPS-INAF, Roma. We thank Dr. D. Blake of
NASA Ames for access to the SEM for imaging and Dr. A. Brown
(SETI) for his invaluable assistance in obtaining the SEM imaging.
Moreover authors want to thanks Prof. E. Cloutis and an anonymous
reviewer for their pertinent comments and suggestions that
helped us to more clearly set the manuscript.
C. Carli wants to thanks T.L. Roush and Ames Research Center
for hosting him during his month-long visit.
This work was financially supported by Agenzia Spaziale Italiana,
SIMBIO-SYS project.
Abstract
Silicate glasses with igneous compositions can be an important constituent of planetary surface material via effusive volcanism or impact cratering processes. Different planetary surfaces are mapped with hyper-spectrometers in the VNIR, and in this spectral range crystal field absorptions are useful in discriminating iron bearing silicate components. For these reasons studying glassy materials, and their optical constants, is an important effort to better document and understand spectral features of Solar System silicate crusts where glasses are present, but may be difficult to map. In our work we present a set of four different synthetic glasses, produced under terrestrial conditions, with variable composition and in particular an increasing amount of iron. The VNIR spectra show, for all the compositions, two absorptions are present near 1.1 and 1.9 μm but reflectance, slope and absorption shape varies with composition. We measured the reflectance of different particle sizes of the samples and used radiative transfer models to estimate the optical constants as a function of wavelength. We used the retrieved optical constants to estimate the particle size from the measured reflectances and the results fall within the known sieve range. We qualitatively discuss the effect of the shape and distribution of particles on the application of the model.
Volume
266
Start page
267
Issn Identifier
0019-1035
Ads BibCode
2016Icar..266..267C
Rights
open.access
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