Isotopic Evidence for a Cold and Distant Origin of 3I/ATLAS (Cordiner et al. 2026): JWST Data and PSG scripts

This archive contains the data and input files required to reproduce the radiative transfer modeling of the JWST data of comet 3I/ATLAS, as used in the article "Isotopic Evidence for a Cold and Distant Origin of 3I/ATLAS" by Cordiner et al. (2026), which was accepted for publication in Nature in June 2026. These files should be used in conjunction with the online (or local) version of the NASA Planetary Spectrum Generator. Using the graphical interface available at https://psg.gsfc.nasa.gov, click "Select template" --> "Upload config file", then browse to select the desired .cfg file from the molecular subdirectories, for the spectral extraction region (annulus) of interest. Then click "Retrievals" at the top, then "Retrieve". The relevant JWST data and retrieval parameters are packaged together inside the .cfg files. The calibrated JWST NIRSpec IFU data cubes for 3I/ATLAS, observed 2025 Dec 22-23 for the wavelength ranges applicable to the present article, are stored in G235H_cube.fits and G395H_subCube.fits, and are readable using standard astronomical software visualisation packages.