Supplemental data and figures behind: Atomic-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), es..., 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. , Any free imaging software can be used to open these files. , # Supplemental data and figures behind: Atomic-scale element and isotopic investigation of 25Mg-rich stardust from a H-burning supernova

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Uploaded is ion imaging, scanning electron microscopy (SEM) imaging and atom probe tomography (APT) reconstruction and spectra.

## Description of the data and file structure

This is the processed data from which the figures and relationships were determined. The spectra from APT can be used for studying chemistry in the measured presolar grain (uploaded as a jpeg), ion images can be used for determining its isotopic signature (exported from NanoSIMS data processing software and uploaded as a jpeg), and SEM images give local context and a visual look at the identified grain in this study. The SEM images are BSE images of the presolar grain in the mineral matrix in ALH 77307.

The Excel document details the isotopic calculations. The first tab has Mg and Si isotopic values determined using Atom Probe Tomography and which peaks were used for the c...