Characterization of micrometerorites from Roysane and Nils Larsen, Sør Rondane Mountains (East Antarctica) 

Characterization of micrometerorites from Roysane and Nils Larsen, Sør Rondane Mountains (East Antarctica)Zelinsky1, C., Krämer Ruggiu1, L., Boschi1, S., Binu Beena1, D., Debaille2, V., Schönbächler3, M., Valdes4,5, M., Heck4, P. R., Goderis1, S.1Archaeology, Environmental Changes, and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels 2 Laboratoire G-Time, Université libre de Bruxelles, Avenue F.D. Roosevelt, 50 1050, Brussels  3 Institut für Geochemie und Petrologie, ETH Zürich, Clausiusstrasse 25, 8092 Zürich 4 Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605, United States  5 The School of the Art Institute of Chicago, Chicago, IL 60603, United States  Each year ~5000 tons of extraterrestrial (ET) material accrete to Earth [1] with the majority consisting of small dust particles with size fractions of 2000 down to 10 µm, termed micrometeorites (MM). MMs are mainly thought to originate from evaporation tails of cometary bodies or to be produced during collision breakup events in the asteroid belt [2]. Despite their small size textural, chemical, and isotopic analysis of MMs has proven to be valuable in estimating Earth’s ET dust intake, reconstructing dust producing events in the Solar System, such as collision breakups of asteroids [3] and the convergence of new comets [4] and identifying potential parent body sources [5]. To provide a sturdy baseline for MM research and to mark MMs as a reliable tool in reconstructing the extraterrestrial influx over geological timescales, first, modern, well-preserved MMs need to be characterized in detail. Different sample locations in Antarctica have proven to be reliable sampling grounds as arid environments limit weathering effects and anthropogenic contamination is restricted [6]. Compared to melting snow and ice, sedimentary traps ensure an accumulation of sampling material over extended periods of time and relatively easy access.  One issue in MM research is inconsistent sample extraction and preparation rendering a direct comparison between different MM collections challenging. This project aims at comparing MMs from a wide range of sample locations across Antarctica to provide a more robust baseline of modern MMs. This study mainly focusses on the not yet studied sample sites of Roysane and Nils Larsen, both small moraines situated in the south-west of the Sør Rondane Mountains in East Antarctica and compares these to other Antarctic collections both in the Sør Rondane Mountains and beyond. Thorough petrographic characterization is first applied to identify different MM types, reconstruct the overall material flux to Earth, account for possible weathering effects and preservation of individual MMs. Major- and trace-element analysis via EPMA and LA-ICP-MS is used to compare weathering effects and constrain peak temperatures during atmospheric entry heating [7]. Triple-oxygen analysis via SIMS (Secondary Ion Mass Spectrometry) aids in refining atmospheric entry processes possible parent body source materials as oxygen isotope compositions vary significantly between distinct chondrite subclasses [7] and can therefore link individual MMs to various parent bodies. Although this study focuses on sample locations Nils Larsen and Roysane, other Antarctic collections such as Widerøefjellet and Walnumfjellet are processed in parallel to account for differences in physiochemical properties and sedimentary host deposits between sample locations [8, 9]. Ultimately, this combined effort will aid in providing a reliable and consistent baseline for MM studies and in obtaining a better understanding of the overall ET flux to Earth, potential parent bodies and interaction dynamics between Earth and the Solar System.    References:[1] Rojas et al., 2021, Earth Planet. Sci. Lett. 560, 116794.[2] Suttle and Folco, 2020, J. Geophys. Res. Planets 125, 1–18.[3] Farley et al., 2006, Nature, 439, 295–297.[4] Genge, 2017, Geophys.Res. Lett., 44, 1679–1686.[5] Suavet et al., 2010, Earth. Planet. Sci. Lett., 293, 313-320.[6] Suavet et al., 2009, Polar Sci. 3, 100–109.[7] Cordier et al., 2011, Geochim. Cosmochim. Acta 75 (2011) 5203–5218.[8] Goderis et al., 2020, Geochim. Cosmochim. Acta 270 (2020) 112–143.[9] Schmitz et al., 2019, Sci. Adv. 5, 1–11.