The James Webb Space Telescope has observed the interstellar comet 3I/ATLAS for the first time, using its infrared instruments to study the comet’s size, composition, and outgassing.

Discovered in July 2025, 3I/ATLAS is the third known interstellar visitor, and JWST detected unusually high levels of carbon dioxide along with water, carbon monoxide, and carbonyl sulfide in its coma.

The comet’s composition may reveal the conditions of its formation around another star, possibly near a “carbon dioxide ice line,” and its low water vapor suggests heat struggles to penetrate its icy core, Space.com has reported.

At an estimated 7 billion years old, 3I/ATLAS is the oldest comet ever observed, and ongoing JWST observations aim to uncover more about its origin and structure before it exits the solar system.