Presolar Silicon Carbide in Oued Chebeika 002 and Other CI Materials

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Nittler L. R.* Meraviglia H. Alexander C. M. O’D. Kulenguski A. S. H. Stroud R. M.

METSOC 2026 abstract (PDF)

“Presolar grains from / New CI are typical / Unlike in Bennu.”

“Two important observations may be made: 1) the Ryugu, Bennu, and OC002 data all show a lack of highly 14N-rich grains that dominate the literature data on purified SiC. This almost certainly reflects the contribution of isotopically normal or heavy N from surrounding material in the in-situ/IOM data. The OC002 data show the smallest range of anomalies, certainly reflecting a more severe contamination problem from the surrounding IOM. 2) The Bennu data are fundamentally different from all other presolar SiC data, showing both a higher fraction of highly 13C- and 15N-rich grains and an unusual cluster of 13C-poor, ~normal-N grains (ellipse: 6.6% of Bennu SiC compared to essentially none in the literature data). Since the isotopic distributions of presolar SiC are closely similar among all other meteoritic samples (including CIs), if correct, this implies that Bennu cannot be genetically related to CIs or other chondrite groups and an explanation in terms of the origin and evolution of the early Solar System is needed. Analysis of purified SiC grains from Bennu is needed to determine if the unusual data reported so far are due to laboratory artifacts related to in-situ analysis of N isotopes in the presence of abundant 15N-rich organic matter [13].

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