Geological characterization of remote field sites using visible and infrared spectroscopy: Results from the 1999 Marsokhod field test

Upcoming Mars Surveyor lander missions will include extensive spectroscopic capabilities designed to improve interpretations of the mineralogy and geo logy of landing sites on Mars. The 1999 Marsokhod Field Experiment (MFE) wa s a Mars rover simulation designed in part to investigate the utility of vi sible/near-infrared and thermal infrared field spectrometers to contribute to the remote geological exploration of a Mars analog field site in the Cal ifornia Mojave Desert. The experiment simultaneously investigated the abili ties of an off-site science: team to effectively analyze and acquire useful imaging and spectroscopic data and to communicate efficiently with rover e ngineers and an on-site field team to provide meaningful input to rover ope rations and traverse planning. Experiences gained during the MFE regarding effective communication between different mission operation teams will be u seful to upcoming Mars mission teams. Field spectra acquired during the MFE mission exhibited features interpreted at the time as indicative of carbon ates (both dolomitic and calcitic), mafic rocks and associated weathering p roducts, and silicic rocks with desert varnish-like coatings. The visible/n ear-infrared spectra also suggested the presence of organic compounds, incl uding chlorophyll in one rock. Postmission laboratory petrologic and spectr al analyses of returned samples confirmed that all rocks identified as carb onates using field measurements alone were cafe-silicates and that chloroph yll associated with endolithic organisms was present in the one rock for wh ich it was predicted. Rocks classified from field spectra as silicics and w eathered mafics were recognized in the laboratory as metamorphosed monzonit es and diorite schists. This discrepancy was likely due to rock coatings sa mpled by the field spectrometers compared to fresh rock interiors analyzed petrographically, in addition to somewhat different surfaces analyzed by la boratory thermal spectroscopy compared to field spectra.