Analysis of Lunar Meteorites

Meteorites from the Moon provide key information about the Moon that beautifully complements information gained from the Apollo missions and samples, and from recent global remote sensing of the Moon. Lunar meteorites now surpass the Apollo sample collection in the mass of meteorite material known to be from the Moon (see the fabulous website maintained by our colleague Randy Korotev).

We work closely with our colleague Tony Irving to help classify meteorites, many of which are lunar. In some cases, we are able to do additional petrographic and petrologic work to characterize the meteorites, e.g., Chen, et al. (2019) Petrogenesis and shock metamorphism of basaltic lunar meteorites Northwest Africa 4734 and 10597. J. Geophys. Res. Planets 124, 2583-2598. https://doi.org/10.1029/2019JE006084. Here we feature work being done by graduate student Chris Yen on basaltic lunar meteorite NWA 12384 (see Fig. to the left).

(a) Partially cross-polarized transmitted light photomicrograph of a polished section of NWA 12384 (PTS-1), photo by N. Buckland. (b) Backscattered electron image composite of NWA 12384 with labeled and outlined clasts. (c) X-ray composite RGB image with Al in the red channel, Mg in the in the green channel, and Fe in the blue channel.

Chris is a third-year Ph.D. grad student working in planetary geology on petrographic and geochemical analysis and classification of lunar rocks, including lunar meteorites, using electron probe microanalysis (EPMA) and X-ray imaging. Chris has used skills gained doing planetary remote sensing to analyze quantitative EPMA compositional maps in an innovative way. In his study of NWA 12384, a complex lunar meteorite with basaltic clasts and picritic glass beads, he has also done work in experimental petrology and crystallization modeling. We seek to connect results from sample analysis to larger scale remote-sensing observations such as using LROC-derived TiO2 data to search the Moon for locations that might have been the launch site for NWA 12384. Here is an example of the mineralogical classification from EPMA x-ray image analysis, zoomed in (left) to show an individual complex pyroxene phenocryst, and zoomed out (right) to show more of the main pigeonite basalt clast noted in the figure above. See the LPSC 52 abstract for more information.

Mineralogic classification map of a pyroxene hopper crystal in NWA 12384, overlaid on a high-resolution backscattered electron image. The core is an aggregate of plagioclase (red), augite (blue, yellow, and cyan), and ilmenite. The phenocryst is zoned, with a pigeonite core (green) and an augite rim (blue).
Full mineralogical classification map of a portion of the large basalt clast in NWA 12384. The phenocryst on the middle-right is the one depicted in the figure above.