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[ 1 ] The Miniature Thermal Emission Spectrometer (Mini-TES) on board the Mars Exploration Rover Spirit is part of ap ayload designed to investigate whether al ake once existed in Gusev Crater.M ini-TES has observed hundreds of rocks along the rover's traverse into the Columbia Hills, yielding information on their distribution, bulk mineralogy,a nd the potential role of water at the site. Although dust in various forms produces contributions to the spectra, we have established techniques for dealing with it. All of the rocks encountered on the plains traverse from the lander to the base of the Columbia Hills share common spectral features consistent with an olivine-rich basaltic rock known as Adirondack Class. Beginning at the base of the West Spur of the Columbia Hills and across its length, the rocks are spectrally distinct from the plains but can be grouped into ac ommon type called Clovis Class. These rocks, some of which appear as in-place outcrop, are dominated by ac omponent whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration. The northwest flank of Husband Hill is covered in float rocks known as Wishstone Class with spectral features that can be attributed uniquely to plagioclase feldspar,aphase that represents more than half of the bulk mineralogy.R are exceptions are three classes of basaltic ''exotics''f ound scattered across Husband Hill that may represent impact ejecta and/or float derived from local intrusions within the hills. The rare outcrops observed on Husband Hill display distinctive spectral characteristics. The outcrop called Peace shows af eature attributable to molecular bound water,a nd the outcrop that hosts the rock called Watchtower displays ad ominant basaltic glass component. Despite evidence from the rover's payload for significant alteration of some of the rocks, no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by Mini-TES. The mineralogical results supplied by Mini-TES provide no clear evidence that al ake once existed in Gusev Crater.

[1] The Mars Exploration Rovers investigated numerous craters in Gusev crater and Meridiani Planum during the first $400 sols of their missions. Craters vary in size and preservation state but are mostly due to secondary impacts at Gusev and primary impacts at Meridiani. Craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes. Effects of gradation on crater form are dependent on size, local lithology, slopes, and availability of mobile sediments. At Gusev, impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks. Ejecta initially experience eolian stripping, which becomes weathering-limited as lags develop on ejecta surfaces and sediments are trapped within craters. Subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting. At Meridiani the sulfate-rich bedrock is more susceptible to eolian erosion, and exposed crater rims, walls, and ejecta are eroded, while lower interiors and low-relief surfaces are increasingly infilled and buried by mostly basaltic sediments. Eolian processes outpace early mass wasting, often produce meters of erosion, and mantle some surfaces. Some small craters were likely completely eroded/buried. Craters >100 m in diameter on the Hesperian-aged floor of Gusev are generally more pristine than on the Amazonian-aged Meridiani plains. This conclusion contradicts interpretations from orbital views, which do not readily distinguish crater gradation state at Meridiani and reveal apparently subdued crater forms at Gusev that may suggest more gradation than has occurred.

We present the results of a combined study of shocked labradorite from the Lonar crater, India, using optical microscopy, micro-Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, high-energy X-ray total scattering experiments, and micro-Fourier transform infrared (micro-FTIR) spectroscopy. We show that maskelynite of shock class 2 is structurally more similar to fused glass than to crystalline plagioclase. However, there are slight but significant differences-preservation of original preimpact igneous zoning, anisotropy at infrared wavelengths, X-ray anisotropy, and preservation of some intermediate range order-which are all consistent with a solid-state transformation from plagioclase to maskelynite.