WARD, Jennifer ('01) (Advisor: Rich April)
The surface coatings on terrestrial basalts were studied as a possible tool for understanding the surface composition of Mars. X-ray diffraction and petrographic and scanning electron microscopy were used to examine basalt samples from near Flagstaff, Arizona and Las Vegas, Nevada. Optical and x-ray diffraction analyses showed that the bulk compositions of the samples were similar, dominated by sodium-rich plagioclase and diopside with minor amounts of ilmenite and hornblende. The compositions of the surface coating and the bulk rock of the SP Crater sample were found to be similar, suggesting that this coating is a weathering rind rather than a desert varnish. The Black Mesa sample is varnished, as indicated by the presence of manganese and iron oxides in the coating. However, the thermal infrared spectra (5-25 µm) collected for both sample coatings were indistinguishable. Therefore, it can be concluded that varnished rocks and rocks exhibiting glassy rinds will look the same to a thermal infrared spectrometer. This suggests that if such rocks exist on Mars, other methods or wavelength ranges will be needed in order to differentiate between these two rock types.
