| This dissertation focuses on two topics; 1) quantifying the effects of roughness on the thermal infrared spectra of rock surfaces and 2) the identification and geologic context of proposed chloride-bearing materials on the Martian surface. Using thermal infrared (TIR) multi-spectral and hyperspectral data in concert with elevation and geomorphological information, I investigated the composition and global distribution of spectrally distinct surfaces on Mars. Based on the spectral observations, in concert with ancillary geomorphological observations, I concluded that the spectrally distinct deposits contained a component attributable to chloride-salts. The materials are predominantly local in nature, yet their prevalence across the southern highlands suggests that they represent one or more globally ubiquitous process and that formation of chloride salts on Mars has been an important process. I also present the results of a laboratory study that focuses on systematically, under controlled conditions, investigating the effects of rough surfaces on the infrared spectra of different natural rock samples. The results indicate that: 1) the roughening process is highly repeatable across rock types, 2) rock types vary in the degree that they are susceptible to abrasion, 3) features in emissivity spectra do not change shape or position with increasing surface roughness, 4) reduction of spectral contrast is observed with increasing roughness across all rock groups until a threshold roughness (which varies across rock types) is achieved, whereupon further reductions do not occur or in some cases, spectral contrast begins to increase, 5) spectra from the roughened surfaces are well explained by few surface reflections, and 6) I do not observe complete obscuration of features in any of our roughened spectra, and 7) surfaces created through the roughening process could be considered analogs to materials roughened by aeolian abrasion, a dominant process on the surface of Mars. This study suggests that spectral contrast, strictly speaking, is not dependent upon surface roughness but upon the morphology of the surface. |
