Overview
- On June 22, 2026, teams led by Martin Cordiner published Nature papers reporting JWST and ground‑based measurements that found unusual isotope ratios in 3I/ATLAS.
- Webb’s NIRSpec measured extreme deuterium enrichment in the comet’s water—about an order of magnitude higher than Solar System comets—which models show forms at temperatures near 30 kelvin.
- The comet also shows low carbon‑13 relative to carbon‑12, a pattern astronomers use as a clock for galactic chemical enrichment and which supports an inferred formation epoch of roughly 10–12 billion years ago.
- Key caveats limit certainty: some isotope values, notably nitrogen, carry large uncertainties, the result rests on a single object observed once, and orbital tracing beyond about 10 million years cannot locate a precise birthplace.
- 3I/ATLAS is now outbound on a hyperbolic path and will leave the heliosphere in decades, and researchers say surveys such as the Vera C. Rubin Observatory are needed to find more interstellar samples to test how typical this chemistry is.