VNIR SPECTRAL ROCK CLASSES OBSERVED BY OPPORTUNITY’S PANCAM ON NORTHERN CAPE YORK AND ON MATIJEVIC HILL ON THE RIM OF ENDEAVOUR CRATER, MARS

After its winter-over location at Greeley Haven, the Mars Exploration Rover Opportunity examined the northern tip of Cape York, a portion of the rim of the 22 km diameter Endeavour crater, and performed an extensive examination of a segment of Cape York dubbed Matijevic Hill on which orbital data suggests Mg/Fe smectite clays are located. These portions of Cape York included a number of lithologically distinct units, some of which were also distinct in terms of their visible and near infrared (VNIR) multispectral reflectance spectra as recorded by the rover’s Pancam sensor. There were also smaller materials within these lithologic units that were spectrally distinct. Among the larger lithologic units, windswept or RAT-abraded surfaces of the Grasberg Formation, believed to be the basal sulfate bearing unit in the region, had a broad and deep 900 nm band, nominally attributable to constituent red hematite. The rocks of Matijevic Hill were shot through with veins which displayed a 934 to 1009 nm downturn in reflectance attributed to an H₂O overtone absorption feature in gypsum. This same downturn was also observed in light-toned veins in boxwork features which APXS data indicated contained Al phyllosilicate minerals. This downturn in reflectance would not be consistent with Al phyllosilicate minerals and likely indicates the presence of another phase such as a hydrated silica. Also present on Matijevic Hill were isolated occurrences of hematitic spherules- potentially displaced examples of the hematite concretions, dubbed “blueberries”, ubiquitous on the Meridiani plains, but conceivably produced within the Matijevic Hill rocks. Also within the Matijevic Hill rocks were spherules dubbed “newberries” whose exteriors had spectra like the surrounding matrix materials, but which, when abraded by the RAT had a longer reflectance peak maximum and mildly deeper 535 nm band depth which would be consistent with more oxidized materials within the newberries.