Laboratory and applied studies using thermal infrared spectroscopy and other remote sensing tools for the understanding of the geologic history of Mars

Detailed studies reveal the compositional heterogeneity of the Martian surface and give clues to its geologic history. My work analyzes three compositions or phases. The first is the basaltic composition of intracrater deposits in southwestern Margaritifer Terra. These deposits have higher thermal inertia relative to their surroundings and likely are solid, coherent units. The similarity of the deposits' compositions to that of the region suggests that they were formed from lithification of local basaltic sediments, though the emplacement of primary igneous material is also possible.The second study focuses on detecting and identifying phyllosilicate minerals in thermal infrared (TIR) data. Areas where visible to near-infrared (VNIR) spectra indicate the presence of phyllosilicates show compositional variation in Thermal Emission Imaging System (THEMIS) TIR images consistent with phyllosilicate. Thermal Emission Spectrometer (TES) TIR spectra in our study regions are modeled by phyllosilicate near the 10--15% detection limit of the technique. Though TES TIR spectra indicate that the compositions differ from the surrounding regions, the differences are not caused solely by changes in phyllosilicate abundance. We suggest that a phase not included in the spectral library may be used to model phyllosilicates in TES TIR spectra. This could explain the inconsistent trend in phyllosilicate abundance that we observe.The third part of my work is a fundamental laboratory analysis of chert and amorphous silica. Their spectral character varies in the TIR and VNIR. Chert and amorphous silica spectra differ in the TIR region but may be similar in the VNIR region. Factors such as surface roughness and incidence angle cause variation in the TIR spectra, but the variation is non-unique. We do not find an obvious way to link spectral character to environment of formation. At TES spectral resolution silica phases may be distinguished from one another but this is more difficult at THEMIS resolution. Spectral indices in the VNIR may not detect all occurrences of chert and amorphous silica, especially if the VNIR spectrum has no features. When applied to three high-silica sites on Mars, this new information confirms that they are dominated by chert or coarsely crystalline quartz.