Publication Date:
2019-06-28
Description:
Spectral data for smectite clays, particularly for montmorillonite, which contain various adsorbed ions and are measured in the UV, VIS, and NIR ranges are analyzed and compared with Martian soil and dust spectra. It is shown that the structural octahedral iron in smectite clays affects their light absorbance in the UV at 240-260 nm, which results from an O(2-) to Fe(3+) charge transfer, similar to one observed in the Martian spectrum. Adsorbed iron affects, via crystal field absorptions, the reflectance of montmorillonite in the VIS and NIR ranges, resulting in stronger absorption and higher opacity in the range 0.40-0.65 micron. Both in spectral contrast and presence of (or lack of) spectral features, the Fe-montmorillonite spectra in the VIS and NIR are in reasonable agreement with the Martian spectrum. It is found that the spectral characteristics of iron-saturated smectite clays cannot be used to preclude the presence of clays in Martian soils and dust.
Keywords:
LUNAR AND PLANETARY EXPLORATION
Type:
Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C771-C77
Format:
text
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