Abstract-Lunar mare basalt sample data suggest that there is a bimodal distribution of Ti02 concentrations. Using a refined technique for remote determination of Ti02, we find that the maria actually vary continuously from low to high values. The reason for the discrepancy is that the nine lunar sample return missions were not situated near intermediate basalt regions. Moreover, maria with 2-4 wt% Ti02 are most abundant, and abundance decreases with increasing Ti02. Maria surfaces with Ti02 >5 wt% constitute only 20% of the maria. Although impact mixing of basalts with differing Ti concentrations may smear out the distribution and decrease the abundance of high-Ti basalts, the distribution of basalt Ti contents probably reflects both the relative abundances of ilmenite-free and ilmenite-bearing mantle sources. This distribution is consistent with models of the formation of mare source regions as cumulates from the lunar magma ocean.

[1] The volcanic domes, cones, sinuous rilles, and pyroclastic deposits of the Marius Hills region of the Moon (~13.4 N, 304.6 E) represent a significant episode of magmatic activity at or near the lunar surface that is still poorly understood. Comparisons between LROC NAC block populations, Mini-RF data, and Diviner-derived rock abundances confirm that blocky lava flows comprise the domes of the Marius Hills. 8 mm features measured by Diviner indicate that the domes are not rich in silica and are not significantly different than surrounding mare materials. LROC observations indicate that some of the dome-building lava flows originated directly from volcanic cones. Many of the cones are C-shaped, while others are irregularly shaped, and local topography and lava eruptions affect cone shape. In general, the cones are morphologically similar to terrestrial cinder and lava cones and are composed of varying amounts of cinder, spatter, and lava. Many of the cones are found in local groupings or alignments. The wide range of volcanic features, from broad low domes to steep cones, represents a range of variable eruption conditions. Complex morphologies and variable layering show that eruption conditions were variable over the plateau.

[1] We used a Lunar Reconnaissance Orbiter Camera (LROC) global monochrome Wide-angle Camera (WAC) mosaic to conduct a survey of the Moon to search for previously unidentified pyroclastic deposits. Promising locations were examined in detail using LROC multispectral WAC mosaics, high-resolution LROC Narrow Angle Camera (NAC) images, and Clementine multispectral (ultraviolet-visible or UVVIS) data. Out of 47 potential deposits chosen for closer examination, 12 were selected as probable newly identified pyroclastic deposits. Potential pyroclastic deposits were generally found in settings similar to previously identified deposits, including areas within or near mare deposits adjacent to highlands, within floor-fractured craters, and along fissures in mare deposits. However, a significant new finding is the discovery of localized pyroclastic deposits within floor-fractured craters Anderson E and F on the lunar farside, isolated from other known similar deposits. Our search confirms that most major regional and localized low-albedo pyroclastic deposits have been identified on the Moon down to $100 m/pix resolution, and that additional newly identified deposits are likely to be either isolated small deposits or additional portions of discontinuous, patchy deposits.

No abstract

[1] The Lunar Reconnaissance Orbiter Camera (LROC) is systematically imaging impact melt deposits in and around lunar craters at meter and sub-meter scales. These images reveal that lunar impact melts, although morphologically similar to terrestrial lava flows of similar size, exhibit distinctive features (e.g., erosional channels). Although generated in a single rapid event, the post-impact mobility and morphology of lunar impact melts is surprisingly complex. We present evidence for multi-stage influx of impact melt into flow lobes and crater floor ponds. Our volume and cooling time estimates for the postemplacement melt movements noted in LROC images suggest that new flows can emerge from melt ponds an extended time period after the impact event. Citation: Bray, V. J., et al. (2010), New insight into lunar impact melt mobility from the LRO camera, Geophys.