CONSTRAINING THE FORMATION OF THE LUNAR ANORTHOSITIC CRUST WITH MOON MINERALOGY MAPPER AND DIVINER LUNAR RADIOMETER EXPERIMENT DATA

The study of Apollo samples spawned the lunar magma ocean concept, predicting that the lunar crust - referred to as the primary anorthositic crust - formed by floatation of plagioclase after approximately 70 % of solidification of the magma ocean [1-3]. However, this simple concept does not explain the observed surface compositional heterogeneities highlighted by several remote sensing datasets and analyses of Apollo samples and lunar meteorites. In this survey, we aim at providing constraints to the formation of the anorthositic crust using two spectroscopic compositional datasets: visible near-infrared (VNIR) data from the Moon Mineralogy Mapper (M³), and thermal infrared (TIR) observations from the Diviner Lunar Radiometer Experiment (Diviner) data. M³ is a hyperspectral imager that orbited the Moon between 2008 and 2009 with 85 spectral channels and a spatial resolution of 140 or 280 m/pixel [4]. Level 2 data from the Planetary Data System (PDS) were used and the ground truth correction developed by [5] was applied. Diviner is a nine-channel radiometer onboard the Lunar Reconnaissance Orbiter (LRO) which launched in 2009 and is acquiring data with a spatial resolution of ~200 m [6]. Level 3 Diviner data from the PDS were used. The three TIR channels near 8 µm are used to measure the Christiansen feature (CF) position, which changes systematically with silicate mineralogy [7, 8]. The CF position of the plagioclase solid solution endmembers is different, shifting from ~7.52 µm for albite [9] to ~7.84 µm for anorthite [10]. Preliminary results will be reported on two complex impact craters located in the anorthositic highlands. Nearly pure plagioclase detections (> 99-100 vol% plagioclase) were reported on their central peaks in the literature: Jackson and Vavilov Craters [10]. Regions of interest were created on the pure-plagioclase areas, and CF position was extracted over these areas in order to constrain to their compositional range, and help in identifying their anorthosite family (ferroan, Mg-suite of alkali anorthosites).

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