Supplemental data and figures behind: Atom scale element and isotopic investigation of 25Mg-rich stardust from a H-burning supernova

We have discovered a presolar olivine from ALH 77307 with the highest 25Mg isotopic composition measured in a silicate to date (δ25Mg = 3025.1‰ ± 38.3‰). Its isotopic compositions challenge current stellar models, with modelling of Mg, Si and O showing a closest match to formation in a supernova where hydrogen ingestion occurred in the pre-supernova phase. Presolar grains within primitive astromaterials retain records of processes and environmental changes throughout stellar evolution. However, accessing these records has proved challenging due to the average grain size (~150 nm) of presolar silicates, their sensitivity to extraction agents and instrumental restrictions, limiting the range of isotopic and chemical signatures which can be studied per grain volume. Here, we present the first known detailed, geochemical study of a presolar silicate from a H-burning supernova, studied in 3D without contributions to the analysis volume and at unprecedented spatial resolutions (< 1 nm), essential for constraining physical and chemical processes occurring within this recently proposed stellar environment. From our results, we infer either; [1] condensation within an environment depleted of heavy elements compatible with the olivine lattice under the pressure and temperature conditions during condensation. [2] during periods of limited mixing either near the end of the pre-supernova phase or from a collapse so rapid localised pockets of different gas compositions formed.

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Funding provided by: Australian Research CouncilAward Number: ARC Laureate fellowship programme
Funding provided by: Department of EducationCrossref Funder Registry ID: https://ror.org/03z942k20Award Number:

NanoSIMS (Secondary ion mass spectrometry) ion imaging was conducted with the CAMECA (Compagnie des Applications Mécaniques et Electroniques au Cinéma et à l'Atomistique) NanoSIMS 50L ion probe at the Centre for Microscopy, Characterisation, and Analysis (CMCA), University of Western Australia. Data was processed using custom in-house software at JSC. See the methods section of the associated manuscript for details.

Atom probe tomography data was collected using the CAMECA Local Electrode Atom Probe, LEAP 4000X HR, within the Geoscience Atom Probe facility, at the JdLC, Curtin University. Data was processed using the Atom Probe (AP) Suite 6.0 processing software and Integrated Visualization and Analysis Software (IVAS) 3.8. Experimental conditions, acquisition parameters, data reconstruction parameters and data processing methods are detailed within the methods of the associated manuscript.