TY - JOUR
T1 - Reflectance spectroscopy (0.35-8μm) of ammonium-bearing minerals and qualitative comparison to Ceres-like asteroids
AU - Berg, Breanne L.
AU - Cloutis, Edward A.
AU - Beck, Pierre
AU - Vernazza, Pierre
AU - Bishop, Janice L.
AU - Takir, Driss
AU - Reddy, Vishnu
AU - Applin, Daniel
AU - Mann, Paul
N1 - Funding Information:
We would like to thank Wendy Calvin (University of Nevada) for providing sample PLG138 from Cuprite, Nevada, as well as Stan Mertzman (Franklin and Marshall College) for the elemental combustion analysis results. We also wish to thank Dr. Carlé Pieters and Dr. Takahiro Hiroi for measuring a number of the reflectance spectra used in this study and for providing open access to data acquired at the NASA-supported RELAB multi-user spectroscopy facility at Brown University. The University of Winnipeg’s HOSERLab was established with funding from the Canada Foundation for Innovation , the Manitoba Research Innovations Fund and the Canadian Space Agency , whose support is gratefully acknowledged. This study was supported by research grants from NSERC , the Canadian Space Agency and the University of Winnipeg . Finally, we wish to thank the comments and suggestions provided by two anonymous reviewers that greatly improved the quality of this paper.
Publisher Copyright:
© 2015 Elsevier Inc.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - Ammonium-bearing minerals have been suggested to be present on Mars, Ceres, and various asteroids and comets. We undertook a systematic study of the spectral reflectance properties of ammonium-bearing minerals and compounds that have possible planetary relevance (i.e., ammonium carbonates, chlorides, nitrates, oxalates, phosphates, silicates, and sulfates). Various synthetic and natural NH4+-bearing minerals were analyzed using reflectance spectroscopy in the long-wave ultraviolet, visible, near-infrared, and mid-infrared regions (0.35-8μm) in order to identify spectral features characteristic of the NH4+ molecule, and to evaluate if and how these features vary among different species. Mineral phases were confirmed through structural and compositional analyses using X-ray diffraction, X-ray fluorescence, and elemental combustion analysis. Characteristic absorption features associated with NH4 can be seen in the reflectance spectra at wavelengths as short as ~1μm. In the near-infrared region, the most prominent absorption bands are located near 1.6, 2.0, and 2.2μm. Absorption features characteristic of NH4+ occurred at slightly longer wavelengths in the mineral-bound NH4+ spectra than for free NH4+ for most of the samples. Differences in wavelength position are attributable to various factors, including differences in the type and polarizability of the anion(s) attached to the NH4+, degree and type of hydrogen bonding, molecule symmetry, and cation substitutions. Multiple absorption features, usually three absorption bands, in the mid-infrared region between ~2.8 and 3.8μm were seen in all but the most NH4-poor sample spectra, and are attributed to fundamentals, combinations, and overtones of stretching and bending vibrations of the NH4+ molecule. These features appear even in reflectance spectra of water-rich samples which exhibit a strong 3μm region water absorption feature. While many of the samples examined in this study have NH4 absorption bands at unique wavelength positions, in order to discriminate between different NH4+-bearing phases, absorption features corresponding to molecules other than NH4+ should be included in spectral analysis. A qualitative comparison of the laboratory results to telescopic spectra of Asteroids 1 Ceres, 10 Hygiea, and 324 Bamberga for the 3μm region demonstrates that a number of NH4-bearing phases are consistent with the observational data in terms of exhibiting an absorption band in the 3.07μm region.
AB - Ammonium-bearing minerals have been suggested to be present on Mars, Ceres, and various asteroids and comets. We undertook a systematic study of the spectral reflectance properties of ammonium-bearing minerals and compounds that have possible planetary relevance (i.e., ammonium carbonates, chlorides, nitrates, oxalates, phosphates, silicates, and sulfates). Various synthetic and natural NH4+-bearing minerals were analyzed using reflectance spectroscopy in the long-wave ultraviolet, visible, near-infrared, and mid-infrared regions (0.35-8μm) in order to identify spectral features characteristic of the NH4+ molecule, and to evaluate if and how these features vary among different species. Mineral phases were confirmed through structural and compositional analyses using X-ray diffraction, X-ray fluorescence, and elemental combustion analysis. Characteristic absorption features associated with NH4 can be seen in the reflectance spectra at wavelengths as short as ~1μm. In the near-infrared region, the most prominent absorption bands are located near 1.6, 2.0, and 2.2μm. Absorption features characteristic of NH4+ occurred at slightly longer wavelengths in the mineral-bound NH4+ spectra than for free NH4+ for most of the samples. Differences in wavelength position are attributable to various factors, including differences in the type and polarizability of the anion(s) attached to the NH4+, degree and type of hydrogen bonding, molecule symmetry, and cation substitutions. Multiple absorption features, usually three absorption bands, in the mid-infrared region between ~2.8 and 3.8μm were seen in all but the most NH4-poor sample spectra, and are attributed to fundamentals, combinations, and overtones of stretching and bending vibrations of the NH4+ molecule. These features appear even in reflectance spectra of water-rich samples which exhibit a strong 3μm region water absorption feature. While many of the samples examined in this study have NH4 absorption bands at unique wavelength positions, in order to discriminate between different NH4+-bearing phases, absorption features corresponding to molecules other than NH4+ should be included in spectral analysis. A qualitative comparison of the laboratory results to telescopic spectra of Asteroids 1 Ceres, 10 Hygiea, and 324 Bamberga for the 3μm region demonstrates that a number of NH4-bearing phases are consistent with the observational data in terms of exhibiting an absorption band in the 3.07μm region.
KW - Asteroids
KW - Comets
KW - Mars
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U2 - 10.1016/j.icarus.2015.10.028
DO - 10.1016/j.icarus.2015.10.028
M3 - Article
AN - SCOPUS:84946854949
SN - 0019-1035
VL - 265
SP - 218
EP - 237
JO - Icarus
JF - Icarus
ER -