New Estimation of Presolar Grain Abundances in the Paris Meteorite
M. J. Verdier-Paoletti, L. R. Nittler, J. Wang
51st Lunar and Planetary Science Conference (2020), Abstract #2523
“C-rich and O-rich stardust grains have been extensively studied over the last decades [1]. Their isotopic and chemical compositions, as well as their microstructures, have shed light on matterforming processes occurring in their different stellar birthplace, i.e., AGB stars, novae, supernovae and neutron merging events [1]. Their O and C isotope compositions exhibit large deviations from solar values (up to tens of thousands permil) that make them easily distinguishable from the surrounding matrix in meteorites when imaged with the NanoSIMS [1]. However, their mineralogy and small size make them sensitive to aqueous alteration and/or metamorphism on asteroidal parent bodies. Presolar silicates in particular can be easily lost to secondary processes [2] and their abundances within meteorites have consequently been used as tracers of the intensity of those processes [3]. The Paris meteorite exhibits different lithologies with one characterized as a 2.9 [4], which makes Paris the least altered CM chondrite, even though this title might have recently been contested [5,6]. However, presolar silicates appear to be scarce in this meteorite, with an initial study leading to no detection [7]. Last year, we reported the first observations of presolar silicates, oxides and SiC within Paris [8]. However, reported abundances, while consistent with previous CM measurements were still unexpectedly low (22 ppm at most for SiC). Here we report further investigation of our previous dataset as well as a new one acquired on another section. The Paris presolar grain contents were revised upward with abundances above the CM averages for both O-rich and C-rich presolar grains. “
