An unusual interstellar visitor speeding through our solar system was recently spotted by the powerful eye of NASA’s James Webb Space Telescope (JWST).
The American space agency revealed this week that its premier space observatory had captured new images of the comet, known as 3I/ATLAS, on August 6, 2025, using its Near-Infrared Spectrograph instrument.
Since that time, NASA researchers have been studying data collected about the object during Webb’s observations, with the latest insights appearing in a new preprint paper. The latest observations provide further confirmation that 3I/ATLAS is producing a large carbon dioxide-rich cloud of material around the object, commonly referred to as its coma.
Carbon Dioxide in Abundance
The unusual carbon dioxide abundance, previously detected in observations by NASA’s SPHEREx mission, is accompanied by traces of water, carbon monoxide, sulfur compounds, water ice, and an abundance of dust, according to the new findings made possible by Webb.
In the new paper by co-author Martin Cordiner and colleagues, 3I/ATLAS’s unusual ratio of carbon dioxide to water vapor is also noted as having been one of the highest ever measured in a comet. This is significant, as it suggests that 3I/ATLAS is quite distinct from the types of comets that originate within our Solar System.
Unraveling a Comet’s Odd Chemistry
The object’s chemistry is unusual, to say the least, which could mean one of several things. One possibility is that it formed in a region of its home star system where carbon dioxide ice was common. Another possibility is that 3I/ATLAS’s surface ices have been altered by interactions with stronger radiation than typical comets experience.
Additionally, the relatively small amount of water vapor detected around the object may indicate internal conditions that limit the amount of water ice that can sublimate (i.e., turn into gas) compared to the carbon dioxide it contains.
The study’s authors also point out that the dust surrounding 3I/ATLAS is optically thin at the wavelengths observed using the JWST, of which the study’s authors report that the unusual coma “is interpreted as resulting from an enhanced coma dust density in the sunward direction, potentially from the fragmentation of dust grains increasing the scattering.”
An Interstellar Enigma
3I/ATLAS was discovered on July 1, 2025, and has been observed by advanced telescopes around the world since that time. Webb’s recent data have provided some of the latest insights into a space object that has captured the public’s imagination.
In addition to the observations by NASA’s SPHEREx mission, vivid imagery of 3I/ATLAS has also been obtained by Webb’s predecessor, the Hubble Space Telescope.
In a statement released this week announcing the release of the new Webb data, Alise Fisher, speaking from NASA Headquarters in Washington, said that although 3I/ATLAS is not believed to pose any threat to Earth, “NASA’s space telescopes help support the agency’s ongoing mission to find, track, and better understand solar system objects.”
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.