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

[摘要] The past and present weathering processes active at the martian surfacecontrol the chemical and mineralogical nature of the soils. Determining thecurrent characteristics of martian surface materials can, therefore, provide cluesabout the surface history of Mars. The research in this thesis is based on threesets of experiments. First, reflectance spectra are collected from Mars analogmineral samples in the laboratory and compared with spacecraft data. The resultsindicate that the water content of the martian soil is consistent with the 2% valueobtained by the Viking Lander analyses, and this suggests a drier, moredehydrated soil than implied by much modeling of early Mars conditions.Second, ultraviolet radiation-induced dehydration of minerals is investigated as apossible method to convert the postulated large initial supply of hydrated mineralphases on Mars to the current, relatively anhydrous state. These experimentsindicate that water adsorbed onto the surfaces of mineral grains can be ejected byincident ultraviolet photons, but that the removal of bound water from minerals isunlikely to be a significant weathering process on Mars. Thus, the inventory ofhydrous minerals at the surface today is likely representative of the quantity thatformed in the past. Finally, the possibility that ultraviolet radiation can stimulatethe oxidation of materials on the martian surface is studied experimentally. Thedata show that the oxidation rate of metallic iron increases upon exposure to UVphotons but that this process is unlikely to be an effective way to oxidize mineralson Mars. Suggestions for future laboratory experiments and spacecraftinstruments which can further test the conclusions of this thesis are described.

[发布机构] University:California Institute of Technology;Department:Geological and Planetary Sciences

[关键词] Planetary Science and Geology