Lunar and Planetary Laboratory Colloquium
Victoria Hamilton from the Southwest Research Institute will give a talk titled "Distribution, Characteristics and Possible Origin of Adirondack-Class Basalt in Gusev Crater as Observed From Mini-TES Data."
More than 100 unique rock targets belonging to the olivine-rich Adirondack class have been identified using mid-infrared spectra from the Miniature Thermal Emission Spectrometer onboard the Mars Exploration Rover Spirit in Gusev crater. Rare rocks on the west spur of the Columbia Hills and on the plains east of the hills also belong to this class. Hamilton will present evidence that the Adirondack-class basaltic lavas may have had their origin at Apollinaris Tholus.
Linear modeling of Adirondack-class rock spectra shows only minor variations in mineralogy, and the primary phases identified are consistent with olivine basalt having an average olivine composition of ~Fo45. Researchers used factor analysis and target transformation to identify variability within a single class of rocks for the first time, and they found that olivine abundance varies independently of a basaltic matrix.
A spectral component attributable to optically thin dust on rocks has a greater effect on Mini-TES spectra than previously recognized, leading to the conclusion that spectral mixing is not completely linear. This thin dust coating results in the overestimation of sulfate and olivine fractions and the underestimation of plagioclase feldspar, although linear mixing appears to successfully replicate the majority of the observed signal. Published TES spectra of low albedo, low dust cover, olivine-bearing materials do not exhibit the spectral telltales of non-linear behavior, probably because orbital spectra represent mostly mobile regolith that has not accumulated a sufficient dust cover over ~3 x 6 km areas.