NASA’s $10 billion James Webb Space Telescope has made the first-ever observations of interstellar comet 3I/ATLAS, revealing unexpected chemical contents in its halo. The comet, discovered in July, is the third object found drifting through our solar system believed to have originated from another star.
The JWST observed the comet on August 6, 2025, with its infrared vision and NIRSpec instrument. This investigation aims to uncover 3I/ATLAS’s size, physical properties, and chemical makeup. Studying comets like this helps scientists understand what conditions existed in other star systems as they formed.
As expected, the comet is outgassing, creating a characteristic tail and halo. The JWST identified carbon dioxide, water, carbon monoxide, and carbonyl sulfide in its coma. However, an unexpected high ratio of carbon dioxide to water was observed, which could indicate that 3I/ATLAS has a rich carbon dioxide core or formed in a specific region of the protoplanetary disk.
Low water vapor content suggests something within the comet inhibits heat penetration, affecting the transformation rate of carbon dioxide and carbon monoxide. These new findings build upon previous discoveries about 3I/ATLAS, including its estimated age of around 7 billion years, making it the oldest comet ever seen. The JWST will continue to unravel the mystery of this interstellar visitor until it returns to interstellar space.
Source: https://www.space.com/astronomy/james-webb-space-telescope-takes-1st-look-at-interstellar-comet-3i-atlas-with-unexpected-results