Usefulness of weak bands in midinfrared remote sensing of particulate planetary surfaces

Abstract

Midinfrared (2.5–25 μm) reflectance spectra of minerals are often used to predict emittance qualitatively. These spectra display weak overtone and combination tone bands, which may be as diagnostic of composition as the strong fundamental molecular vibration bands usually considered for remote sensing applications, but which have been widely ignored. However, unlike the strong bands, the contrast of weak bands relative to the continuum in the midinfrared usually does not decrease with decreasing particle size, but typically increases. To illustrate this behavior, transmittance and reflectance spectra of calcite and quartz are presented for the wavelength range from 4000 to 400 cm−1 (2.5–25 μm). It is the purpose of this paper to point out that these weak bands are potentially useful for compositional remote sensing of particulate planetary surfaces; this will require completion of supporting laboratory studies to document the occurrence of weak bands.

Effect of Grain Size and Mineral Mixing on Carbonate Absorption Features in the SWIR and TIR Wavelength Regions

“…Carbonate minerals have diagnostic absorption features in the shortwave infrared (SWIR) and thermal infrared (TIR) regions due to vibrational processes of the carbonate ions (CO ) [16][17][18][19][20]. In general, carbonate minerals can be distinguished by the presence of two prominent spectral absorption features in the wavelength ranges around 2.50-2.55 µm and 2.30-2.35 µm in the SWIR [8,18,[20][21][22] and around 13.70-14.04 µm and 11.19-11.40 µm in the TIR [17,19,23,24].…”

“…In general, carbonate minerals can be distinguished by the presence of two prominent spectral absorption features in the wavelength ranges around 2.50-2.55 µm and 2.30-2.35 µm in the SWIR [8,18,[20][21][22] and around 13.70-14.04 µm and 11.19-11.40 µm in the TIR [17,19,23,24]. These features can be used to identify pure and mixed calcite and dolomite in synthetic samples or carbonate rocks, because the absorption band position of calcite is located at a slightly longer wavelength than that of dolomite [8,21].…”

“…These features can be used to identify pure and mixed calcite and dolomite in synthetic samples or carbonate rocks, because the absorption band position of calcite is located at a slightly longer wavelength than that of dolomite [8,21]. Although the absorption band positions of these particular minerals have been observed by multiple researchers, the precise position of calcite and dolomite absorption bands in the SWIR [8,18,21,22] and TIR [19,[23][24][25][26]] spectra has been recorded at different wavelengths.…”

The Earth Observation Technology Cluster

“…The emission spectra from a rock are extremely sensitive to variations in the fabric and bulk chemistry of the rock and the composition of the constituent mineral species, particularly feldspars, garnets, pyroxenes, olivines, and SiO2 minerals (Salisbury et al 1987). FTIR techniques can resolve igneous rock types, clastic and carbonate sedimentary rocks, and sediment grain size and composition (Applegarth and Stefanov 2006).…”

Lunar and Planetary Institute

“…Spectrally, "coarse particles" (e.g., coarse hematite) means large enough to be optically thick (high opacity) [Salisbury et al, 1987], which for hematite is greater than ~1-5 µm over the ~15-50 µm range [EstepBarnes, 1972]. The size at which a material becomes optically thick is tied to the absorptivity.…”