Speaker
Description
Presolar grains are solid stardust particles with very little physical, chemical, or aqueous alteration, making them perfect for direct analysis of stellar processes in the stars that created the material for our solar system. Trace isotopes in presolar grains can tell us about the nucleosynthetic processes occurring in the stars that formed them. Searching for grains in situ can take extensive time, instrumentation use, and requires additional steps to isolate the grain from the meteorite matrix to observe grain morphology. We are using a modified Chicago method [1,2] to chemically separate presolar grains from two meteorites, Murchison and Oued Chebeika 002 (OC 002). Murchison is a well-studied CM chondrite and the source of the majority of published presolar grain data, but OC 002 is a new (2024) find and is the most pristine CI meteorite available [3].
Most meteorites and planets belong to either the carbonaceous (CC) or noncarbonaceous (NC) groups, based on nucleosynthetic isotopic anomalies in many elements. There is growing evidence that the CI meteorites, along with asteroids Ryugu and Bennu (from which samples have been returned to Earth by spacecraft) comprise a third isotopic group; the question arises of whether the CIs have the same population of presolar grains as CCs. Presolar grain separations of CIs have only been completed on Orgueil [4,5]. Through acid treatments, and density and/or size separations, we aim to extract presolar nanodiamonds, refractory minerals, graphite, and silicon carbide. We plan to use nanoscale secondary ion mass spectrometry to quantify isotopic ratios of C, N, and Si on presolar SiC and C and N on graphite grains, which will determine the grain classification [6,7]. Using the CHicago Instrument for Laser Ionization (CHILI) [8], a resonance ionization mass spectrometer, we aim to quantify the isotopic ratios of trace elements affected by branch points in the s-process such as Ba, Mo, Zr, and Sr from the presolar grains extracted in this separation. This will reveal the conditions such as the neutron density or metallicity in neutron capture nucleosynthesis that occurred in the parent stars.
[1] Amari S et al. (1994) Geochim. Cosmochim. Acta 58:459–470. [2] Korsmeyer JM (2025) PhD dissertation, The University of Chicago. [3] Gattacceca J et al. (2025) Meteoritics Planet. Sci. 60:1441–1479. [4] Jadhav M et al. (2013) Geochim. Cosmochim. Acta 113:193–224. [5] Huss and Lewis (1995) Geochim. Cosmochim. Acta 59, 115-160. [6] Amari S et al. (2014) Geochim. Cosmochim. Acta 133:479–522. [7] Stephan T et al. (2024) Astrophys. J. Suppl. Ser. 270:27. [8] Stephan T et al. (2016) Int. J. Mass Spectrom. 407:1–15.
| Career stage | Graduate student |
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