ALBERT

Description: The mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.

Description: Mars Exploration Rover Opportunity is exploring the rim of 22 km diameter, Noachian-aged Endeavour crater. Marathon Valley cuts through the central region of the western rim providing a window into the local lower rim stratigraphic record. Spectra from the Compact Reconnaissance Imaging Spectrometer for Mars show evidence for the occurrence of Fe-Mg smectite in this valley, indicating areally extensive and distinct lithologic units and/or styles of aqueous alteration. The Alpha Particle X-ray Spectrometer has determined the compositions of 59 outcrop targets on untreated, brushed and abraded surfaces. Rocks in the Marathon Valley region are soft breccias composed of mm- to cm-sized darker clasts set in a lighter-toned, finegrained matrix. They are basaltic in non-volatile-element composition and compositionally similar to breccias investigated elsewhere on the rim. Alteration styles recorded in the rocks include: (1) Enrichments in Si, Al, Ti and Cr in more reddish-colored rock, consistent with leaching of more soluble cations and/or precipitation of Si +/- Al, Ti, Cr from fluids. Coprecipitation of Ge-rich phases with Si occurred in the western area only; high water:rock is indicated. Pancam multispectral observations indicate higher nanophase ferric oxide contents, but the rocks have lower Fe contents. The highly localized nature of the red zones indicate they cannot be the source of the widespread smectite signature observed from orbit. (2) Outcrops separated by approximately 65 m show common compositional changes between brushed and abraded (approximately 1 mm deep) targets: increases in S and Mg; decreases in Al, Cl and Ca. These changes are likely due to relatively recent, surface-related alteration of valley rocks and formation of surface coatings under low water:rock. (3) One target, from the center of a region of strong CRISM smectite signature, shows modest differences in composition (higher Si, K; lower Mn) compared to most Marathon Valley rocks, while another target approximately 40 cm away on the same outcrop does not; a change towards smectite bulk compositions is not observed. The smectite signature likely resulted from alteration under low water:rock such that primary minerals were partially altered to phyllosilicates, but wholesale leaching of cations by fluids did not occur.

Description: What are the provenances of the non-mare materials collected at the Apollo and Luna sampling sites? Results from basin ejecta modeling suggest that much of it came from distant basins. Additional information is contained in the original extended abstract.

Description: The detection of reduced carbon in martian rocks and soils is important in the search for evidence of life. A Raman spectroscopic study of South Africa chert reveals that 50 ppm carbon or less can be determined by this technique. Additional information is contained in the original extended abstract.

Description: Compositional remote sensing from the Lunar Prospector mission reveals the Procellarum- Imbrium region of the Moon, also referred to as the Procellarum KREEP Terrane, to be an area of significant enrichment of heat-producing residua (i.e., Thrich) of the early lunar differentiation. Previous estimates place as much as 60-70% of the whole-Moon content of Th into the crust and as much as 35-40% of the crustal Th content into the Procellarum KREEP Terrane [5], which occupies only approx. 10-15% of the volume of the crust. Although these estimates have significant uncertainty, the correspondence of the enrichment of Th (and other heat producers U and K) in this region is consistent with extended igneous activity, manifested at the surface by extensive basaltic volcanism and subdued topography. Such activity may have extended also to a significant depth, probably including the upper mantle. In this abstract, we present evidence based on Apollo samples for some of the most extensively fractionated lunar rocks types, including a Th-rich mare basalt from Apollo 12, and monzogabbro (also known as monzodiorite), granite, and alkali anorthosite from Apollo 12 and 14 samples. We relate these to likely exposures and sources indicated by compositional remote sensing.

Description: Fe-Ti-Cr-Oxide minerals contain much information about rock petrogenesis and alteration. Among the most important in the petrology of common intrusive and extrusive rocks are those of the FeO-TiO2-Cr2O3 compositional system chromite, ulv spinel-magnetite, and ilmenite-hematite. These minerals retain memories of oxygen fugacity. Their exsolution into companion mineral pairs give constraints on formation temperature and cooling rate. Laser Raman spectroscopy is anticipated to be a powerful technique for characterization of materials on the surface of Mars. A Mars Microbeam Raman Spectrometer (MMRS) is under development. It combines a micro sized laser beam and an automatic point-counting mechanism, and so can detect minor minerals or weak Raman-scattering phases such as Fe- Ti-Cr-oxides in mixtures (rocks & soils), and provide information on grain size and mineral mode. Most Fe-Ti-Cr-oxides produce weaker Raman signals than those from oxyanionic minerals, e.g. carbonates, sulfates, phosphates, and silicates, partly because most of them are intrinsically weaker Raman scatters, and partly because their dark colors limit the penetration depth of the excitation laser beam (visible wavelength) and of the Raman radiation produced. The purpose of this study is to show how well the Fe-Ti-Cr-oxides can be characterized by on-surface planetary exploration using Raman spectroscopy. We studied the basic Raman features of common examples of these minerals using well-characterized individual mineral grains. The knowledge gained was then used to study the Fe-Ti-Cr-oxides in Martian meteorite EETA79001, especially effects of compositional and structural variations on their Raman features.

Description: The relatively high concentrations of Th near the Imbrium antipode in the South Pole-Aitken (SPA) basin might represent Imbrium ejecta, a consequence of convergence of Th-rich material ejected by the Imbrium impact that occurred in the Th-rich Procellarum KREEP Terrane. Here, we present landing positions for 7500 fragments ejected from Imbrium obtained by three-body (Earth-Moon-fragment) numerical integration for uniformly selected azimuthal launch positions, ejection angles of 45 deg, and velocities from 0.95 to 0.99 lunar escape. This provides an estimate of the density of infalling ejecta fragments to be expected in the vicinity of the Imbrium antipode. Similar calculations for 35 and 50 deg leave large empty regions surrounding the antipode.

Description: As an aid for interpretation of nuclear data obtained remotely, we provide data on concentrations of oxygen and silicon in a variety of lunar materials.

Description: Raman spectral data are used to distinguish the major structure types and to calculate the major compositional parameters (Mg' and Wo) of quadrilateral pyroxenes. The discrepancies between calculated and measured values are within +/-0.1 cation unit.

Description: We present results of siderophile-element analysis of two FeNi metal grains from the Apollo 16 regolith which each likely crystallized from an impact melt. One is unusual in having a high Ir/Au ratio and high Ga concentration for Apollo 16 metal.