SOLAR SYSTEM — Researchers using the James Webb Space Telescope published detailed findings on June 22, 2026, about the chemical composition of interstellar Comet 3I/ATLAS in the journal Nature. The findings revealed unusual deuterium and carbon isotope levels, indicating the comet's origin outside the solar system.

Comet 3I/ATLAS is the third confirmed interstellar comet and began moving away from the Sun in December 2025. Astronomers used the James Webb Space Telescope to capture detailed measurements of the comet's chemical components. The ATLAS (Asteroid Terrestrial-impact Last Alert System) telescope, funded by NASA, first spotted the object. Researchers received approval to interrupt the space telescope's planned observation schedule to study it, using the NIRSpec (Near-Infrared Spectrograph) instrument to map specific chemical contents.

NIRSpec revealed deuterium levels in Comet 3I/ATLAS approximately 30 times higher than those seen in solar system comets. It also showed only traces of carbon-13 compared to carbon-12. The research team estimates that the comet could have formed 10 to 12 billion years ago.

Martin Cordiner, an astro-chemist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, was the lead author of the study. "This was a unique opportunity to study an ancient object from the distant galaxy, probably pre-dating our Sun and solar system," Cordiner said. "On the one hand, we get direct insight into that distant time and place, and on the other, we learn something about how unusual our own solar system may be."

Stefanie Milam, a co-author of the study and a NASA Goddard researcher, discussed the implications of the findings. "For us as scientists, finding these rare isotopes is fascinating, but the bigger picture here is looking at the possibilities of prebiotic chemistry elsewhere in the galaxy," Milam said. She added, "So far, we know of only one place in the vast cosmos where chemical ingredients led to life – our solar system, our Earth." Analysis of these interstellar objects is a major step towards learning how common, or uncommon, the conditions for the evolution of life are in the universe, Milam stated. The James Webb Space Telescope is an international program led by NASA with partners ESA (European Space Agency) and CSA (Canadian Space Agency).