Variations in Visible/Near-Infrared Hematite Spectra Related to Grain Size and Crystallinity

Johnson, J R ; Cloutis, E ; Fraeman, A A ; Bell, J F III ; Wellington, D ; Horgan, B ; Rampe, E ; Vaniman, D ; Pinet, P

关键词: ABUNDANCE;    AMORPHOUS MATERIALS;    GRAIN SIZE;    HEMATITE;    NEAR INFRARED RADIATION;    SPECTRA;    SPECTRUM ANALYSIS;    VISIBLE SPECTRUM;    CRYSTALLINITY;    CALIBRATING;   

RP-ID  :  JSC-E-DAA-TN66067

学科分类：天文学(综合)

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

Drill fines created by the Curiosity rover at Gale Crater, Mars have exhibited variable visible/near-infrared spectral features attributable to the presence of ferrous and ferric minerals. Drilled locations within the Murray formation and on the Vera Rubin Ridge (VRR) were shown by the CheMin instrument to contain significant amounts of hematite. However, typical hematite spectral features (e.g., absorptions near 530 nm and 860 nm) have varied inconsistently with hematite abundances. This suggests that other factors such as hematite grain size or crystallinity, the presence of amorphous materials, and/or photometric effects play a role in the observed spectra. Using laboratory spectra of hematite acquired at difference grain sizes, we document the variability in key spectral features. We also compare spectral parameters computed from Mastcam spectra on Mars of three hematite-bearing ChemCam calibration target (CCCT) samples with known hematite and amorphous material abundances.