Wow, what a day for preprints (i. e., the arXiv site):
Astrophysics > Earth and Planetary Astrophysics arxiv.org/abs/2603.06911
Cordiner, M. Roth, N. X. Micheli, M. et al. Isotopic Evidence for a Cold and Distant Origin of the Interstellar Object 3I/ATLAS
arxiv.org/abs/2603.07026
Salazar Manzano, L. E. Paneque-Carreño, T. Cordiner, M. A. et al. A Direct View of the Chemical Properties of Water from Another Planetary System: Water D/H in 3I/ATLAS
arxiv.org/abs/2603.07187
Opitom, C. Manfroid, J. Hutsemékers, D. et al. High nitrogen and carbon isotopic ratios in the interstellar comet 3I/ATLAS
arxiv.org/abs/2603.07718
Zhao, R. Zhang, X. Yang, B. et al. Post-perihelion Coma Composition of the Interstellar Comet 3I/ATLAS from Optical Spectroscopy
Standard Disclaimer: I disclaim peer review of arXiv.org.
Carbon, oxygen, and nitrogen are common atoms in Solar System bodies, and comets among them. In particular, forming in the cold, outer Solar System gives a slightly different isotope blend for each element- typically heavier isotopes, like 13C and 15N instead of the usual 12C and 14N. But… 3I ATLAS is not from our Solar System, inner or outer. It formed around another star entirely. To the extent that we get good numbers on ATLAS, we can get a peek at the composition of some other star. Never in my years of schooling did I ever suspect a sample of another star system would fall in here.
And let’s not forget Zhao et al. They cover simple elemental abundances in the tail/coma of ATLAS, not isotopes. Still valid science, like others tracking the comet’s light curve.