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Heterogeneity of Bulk Oxygen Isotopic Compositions in Anhydrous Interplanetary Dust Particles

Anhydrous interplanetary dust particles are among the least altered ancient solar system materials. While hydrous IDPs are 16O-poor, likely due to the interaction with isotopically heavy H2O [1], oxygen isotopes of anhydrous IDPs seem to be highly variable, although data is scarce [2]. Bulk oxygen isotopic compositions of 70 nm thin ultramicrotomed sections of three anhydrous IDPs were measured by NanoSIMS. δ17OSMOW ranges from −24.2 ± 5.4 ‰ (1σ) to 7.8 ± 3.4 ‰ and δ18OSMOW from −25.3 ± 3.6 ‰ to 9.5 ± 3.1 ‰, with the heavier isotopic compositions attributed to the particles that show signs of mild thermal alteration. Isotopic heterogeneity is best explained by contribution of grains sampling different O isotope reservoirs in the protoplanetary disk, created by self-shielding and photodissociation of CO [3]. This process resulted in 16O-rich CO gas and 16O-poor H2O in the outer disk. H2O froze as ice-mantles onto dust grains and evaporated from grains transported to the inner disk, enriching it in 17O and 18O [4]. Therefore, anhydrous IDPs contain a mixture of materials from different times and spaces in the protoplanetary disk, as has been described for material from comet 81P/Wild2 revealed by the STARDUST mission [5].

[1] Keller L.P. and Snead C.J. (2021) LPS LII, Abstract #2389. [2] Starkey N.A. and Franchi I.A. (2013) Geochimica et Cosmochimica Acta 105:73-91. [3] Yurimoto H. and Kuramoto K. (2004) Science 305:1736-1766. [4] Krot A. et al. (2020) Science Advances 6:eaay2724. [5] Brownlee D. (2014) Annual Review of Earth and Planetary Sciences 42:179-205.


Birgit Schulz1, Christian Vollmer1, Lindsay P. Keller2, Peter Hoppe3
1Institut für Mineralogie, Westfälische Wilhelms-Universität Münster, Corrensstr. 24, 48149 Münster, Germany; 2XI3, ARES Division, NASA Johnson Space Center, Houston, TX 77058, USA; 3Max-Planck-Institut für Chemie, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
GeoMinKöln 2022