Degli Alessandrini, Giulia

Gholinia, A

Joy, Katherine

Morland, Zoe

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsMetal Impactor Fragment found in Lunar RegolithBreccia Meteorite North West Africa 10989Conference or Workshop ItemHow to cite:Morland, Zoe; Joy, Katherine; Gholinia, A and Degli Alessandrini, Giulia (2019). Metal Impactor Fragmentfound in Lunar Regolith Breccia Meteorite North West Africa 10989. In: 7th European Lunar Symposium, 21-23 May2019, Manchester, UK.For guidance on citations see FAQs.c© [not recorded]Version: Version of RecordCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukMETAL IMPACTOR FRAGMENT FOUND IN LUNAR REGOLITH BRECCIA METEORITE NORTH WEST AFRICA 10989.  Z. S. Morland1,2, K. H. Joy2, A. Gholinia3 and G. Degli Alessandrini1. 1School of Phys-ical Sciences, Open University, Milton Keynes, UK., 2School of Earth and Environmental Sciences, University of Manchester, UK. 3School of Materials, University of Manchester, UK.  Corresponding email: zoe.morland@open.ac.uk   Introduction:  The composition of material deliv-ered to the inner Solar System throughout history re-mains a mystery [1,2]. Lunar meteorites, unlike sam-ples returned from Apollo and Luna missions, provide a rich resource for understanding the whole surface of the Moon [3]. Here we analyse a recently discovered lunar regolith breccia meteorites, North West Africa (NWA) 10989 (Fig. 1 A), to see whether it holds pre-served impactor material. We consider the implica-tions of its existance under the context of regolith evo-lution and in-situ resource utilisation.  Methods: At the University of Manchester, the petrology of NWA 10989 was analysed using the fol-lowing methods: (1) an ESEM to obtain whole sample merger and close-up BSE images, qualitative EDX point spectra, and whole sample EDS elemental maps; (2) a Raman spectrometer to identify Fe-oxide phases; (3) an EPMA to quantitatively measure major element concentrations; (4) a Broad-ion beam (Argon) mill to polish; and (5) an Oxford Instruments EBSD with AZtec software to study crystallographic structure. Methods: The 1 cm sized fragment of NWA 10989 we investigated specifically contains highland granulites, glassy impact melt breccias (GIMBs), clast-rich impact melt breccias (CIMBs), monomineralic pyroxene and rare mare basalt frag-ments. These clasts are held within a glassy matrix that includes impact melt spherules and Fe-Ni metal. The Fe-Ni metal is dominantly contained within a sin-gle 1.90 × 0.85 mm grain (Metal_1) along with sev-eral other smaller grains and abundant fine particles in the matrix (Figs. 1 A & B).  Results: The metal grains are composed of pre-dominantly kamacite (low-Ni), enriched in K (0.16-0.22 wt%). Metal_1 also contains minor amounts of taenitic (high-Ni) material and K-rich schreibersite. Comparison between the metals’ compositions and the meteoritic field suggest they are similar asteroid-derived meteorite groups, and thus could indicate and exogenous origin [4]. However, silicates in contact with and ocassionally embedded within Metal_1 (Fig. 1 B) reflect native lunar compositions. Metal_1’s internal microstructure consists of an aggregate of 50-150 µm sized variably orientated grains (Fig. 2 A & B). The colour gradients within grains indicate the presence of lattice bending, which in places advanced to sub-grain development.   Discussion: The compositional dichotomy be-tween the native lunar silicates and the sizeable, ap-parently exogenous, Fe-Ni metal suggests either (i) an almost intact fragment of meteorite or (i) a precipitate from an impact melt sheet composed of a vaporised impactor and lunar target rock mixture. Metal_1’s complex internal structure, indicative of crystal plas-tic deformation, could be attributed to strain during regolith reprocessing.  This study advances current knowledge in ISRU through evidence of impactor survival and modifica-tion on the surface of the Moon, plus it aids in under-standing what material was delivered to the inner so-lar system during its history.   Figure 1: (A) Whole sample BSE image, (B) Metal_1 close-up BSE image with EBSD areas shown Figure 2: Inverse pole figures of parts of Metal_1, indicated in Fig. 1 B, where colours represent lattice orientation corresponding to the triangle key.  Acknowledgements: Thanks to Martin Goff, for donating the sample.  References: [1] Hartmann W. et al. (2000) In: R. Canup and K. Righter, eds. Tuscon: University of Ar-izona Press, 805-826. [2] Joy K. H. (2012) Science, 336(6087), 1426-1429. [3] Jolliff B. L. et al. (2000) JGR, 105, 4197-4216. [4] Goldstein J. I. and Yako-witz H. (1971) P. Lunar. Plant. Sci., 2, 177-191. 

Metal Impactor Fragment found in Lunar Regolith Breccia Meteorite North West Africa 10989

http://oro.open.ac.uk/62499/1/Metal%20Impactor%20Fragment%20found%20in%20Lunar%20Regolith%20Breccia%20Meteorite%20North%20West%20Africa%2010989%20ZM_2019.pdf

Metal Impactor Fragment found in Lunar Regolith Breccia Meteorite North West Africa 10989

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