TY - JOUR
T1 - Near-infrared spectra of ferrous mineral mixtures and methods for their identification in planetary surface spectra
AU - Horgan, Briony H N
AU - Cloutis, Edward A.
AU - Mann, Paul
AU - Bell, James
N1 - Funding Information:
We would like to thank Peter Isaacson and Janice Bishop for very helpful reviews, Michelle Minitti for providing glass spectra, Vishnu Reddy for providing OPX–CPXA mixture spectra, Jessica Stromberg for laboratory assistance at the UWPSF, and Lisa Gaddis for helpful advice and comments. This work was supported by funds from the NASA Mars Data Analysis Program, the NASA Harriet G. Jenkins Predoctoral Fellowship, the Arizona State University School of Earth and Space Exploration Postdoctoral Fellowship, the Natural Sciences and Engineering Research Council of Canada, and the Canadian Space Agency. The UWPSF was established with funding from the Canada Foundation for Innovation, the Canadian Space Agency, and the Manitoba Research Innovations Fund.
PY - 2014/5/15
Y1 - 2014/5/15
N2 - Iron-bearing minerals are a major component of planetary surfaces, and many can be identified by their characteristic absorption bands in the near-infrared (NIR). Here we present laboratory NIR spectra of a wide range of common Fe-bearing minerals (e.g., olivines, pyroxenes), glasses, and mineral/glass mixtures. We then use this suite of spectra to evaluate the effects of mixtures on mineral detection methods, including olivine and pyroxene spectral indices developed for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter. We find that although these indices can be compromised by minerals with atypical compositions, mineral mixtures, and the presence of other ferrous minerals, these issues can generally be mitigated by visual inspection of the spectra. However, a special case occurs when the mineral or mixture in question is spectrally indistinguishable from a more common mineral. In particular, we show that spectra of high-calcium pyroxene mixed with Fe-bearing glass can be virtually indistinguishable from common Fe-bearing olivine compositions. This effect, combined with the fact that Fe-bearing glass is generally much more difficult to detect than other ferrous minerals, may be causing glass occurrences on planetary surfaces to be underreported. In support of this hypothesis, we use Mars Express OMEGA observations to show that previous olivine detections in the north polar sand sea on Mars are actually more consistent with local mixing of glass and pyroxene. To address these issues, we present an alternative ferrous mineral identification method based on the position and shape of the 1 and 2μm iron absorption bands, which are sensitive to mineralogy, composition, and mineral mixtures in planetary surface spectra, including glass and mixtures with glass. Using Chandrayaan-1 Moon Mineralogy Mapper (M3) observations of Aristarchus Crater on the Moon, we show that these band parameters can reveal subtle spectral variations and can produce mineralogical maps at an exceptional level of detail.
AB - Iron-bearing minerals are a major component of planetary surfaces, and many can be identified by their characteristic absorption bands in the near-infrared (NIR). Here we present laboratory NIR spectra of a wide range of common Fe-bearing minerals (e.g., olivines, pyroxenes), glasses, and mineral/glass mixtures. We then use this suite of spectra to evaluate the effects of mixtures on mineral detection methods, including olivine and pyroxene spectral indices developed for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter. We find that although these indices can be compromised by minerals with atypical compositions, mineral mixtures, and the presence of other ferrous minerals, these issues can generally be mitigated by visual inspection of the spectra. However, a special case occurs when the mineral or mixture in question is spectrally indistinguishable from a more common mineral. In particular, we show that spectra of high-calcium pyroxene mixed with Fe-bearing glass can be virtually indistinguishable from common Fe-bearing olivine compositions. This effect, combined with the fact that Fe-bearing glass is generally much more difficult to detect than other ferrous minerals, may be causing glass occurrences on planetary surfaces to be underreported. In support of this hypothesis, we use Mars Express OMEGA observations to show that previous olivine detections in the north polar sand sea on Mars are actually more consistent with local mixing of glass and pyroxene. To address these issues, we present an alternative ferrous mineral identification method based on the position and shape of the 1 and 2μm iron absorption bands, which are sensitive to mineralogy, composition, and mineral mixtures in planetary surface spectra, including glass and mixtures with glass. Using Chandrayaan-1 Moon Mineralogy Mapper (M3) observations of Aristarchus Crater on the Moon, we show that these band parameters can reveal subtle spectral variations and can produce mineralogical maps at an exceptional level of detail.
KW - Mars, polar geology
KW - Mars, surface
KW - Mineralogy
KW - Moon, surface
KW - Spectroscopy
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U2 - 10.1016/j.icarus.2014.02.031
DO - 10.1016/j.icarus.2014.02.031
M3 - Article
AN - SCOPUS:84897845491
SN - 0019-1035
VL - 234
SP - 132
EP - 154
JO - Icarus
JF - Icarus
ER -