Published online by Cambridge University Press: 10 December 2009
Two Miniature Thermal Emission Spectrometers (Mini-TES) operated successfully onboard the two Mars Exploration Rovers (MER) on the Martian surface, one at Gusev crater and the other at Meridiani Planum. Designed to provide remotely sensed information on the bulk mineralogy of surface materials, the Mini-TES instruments served to guide the rovers to targets of interest and extrapolate the observations made by the rovers' mechanical-arm-mounted instruments. The Mini-TES on the Spirit rover in Gusev crater observed a flat plain covered by rocks with an olivine-rich ((Mg,Fe)2SiO4) mineralogy and a soil-like unit mantled by airfall dust occurring between the rocks. The dust is a spectral match to dust observed at Meridiani Planum and across the globe. The soil is basaltic in composition, dominated by plagioclase (NaAlSi3O8–CaAl2Si2O8), pyroxene (Ca(Mg,Fe)Si2O6–(Mg,Fe)SiO3), and olivine that probably was produced in part from the breakdown of local rocks. Approximately 2.5 km from the Spirit lander, the Columbia Hills contain a remarkably diverse set of rocks distinct from the plains. Basaltic glass appears to dominate the mineralogy of various outcropping rocks while plagioclase dominates the float rocks that cover most of the north side of Husband Hill, the tallest of the Columbia Hills. Numerous exotic (out of place) rocks dot the hillside that likely were emplaced as impact ejecta in some cases and perhaps as volcanic intrusions in other cases. Onboard the Opportunity rover in Meridiani Planum, the Mini-TES observed a nearly rock-free plain covered in hematite (Fe2O3) spherules and basaltic sand.