Effects of the Martian environment on its surface materials: experimental studies

The past and present weathering processes active at the martian surface control the chemical and mineralogical nature of the soils. Determining the current characteristics of martian surface materials can, therefore, provide clues about the surface history of Mars. The research in this thesis is based on three sets of experiments. First, reflectance spectra are collected from Mars analog mineral samples in the laboratory and compared with spacecraft data. The results indicate that the water content of the martian soil is consistent with the 2% value obtained by the Viking Lander analyses, and this suggests a drier, more dehydrated soil than implied by much modeling of early Mars conditions. Second, ultraviolet radiation-induced dehydration of minerals is investigated as a possible method to convert the postulated large initial supply of hydrated mineral phases on Mars to the current, relatively anhydrous state. These experiments indicate that water adsorbed onto the surfaces of mineral grains can be ejected by incident ultraviolet photons, but that the removal of bound water from minerals is unlikely to be a significant weathering process on Mars. Thus, the inventory of hydrous minerals at the surface today is likely representative of the quantity that formed in the past. Finally, the possibility that ultraviolet radiation can stimulate the oxidation of materials on the martian surface is studied experimentally. The data show that the oxidation rate of metallic iron increases upon exposure to UV photons but that this process is unlikely to be an effective way to oxidize minerals on Mars. Suggestions for future laboratory experiments and spacecraft instruments which can further test the conclusions of this thesis are described.