Interstellar comet 3I/ATLAS happens to be one of the most enthralling topics of discussion lately. To this day, it remains the subject of research and endless discussions, revealing secrets about its origin and composition. What do we know so far?

A new study published in ‘Nature’ suggests that 3I/ATLAS may be one of the oldest cometary objects ever observed, possibly forming 10 to 12 billion years ago. Using observations from the James Webb Space Telescope, supported by data from the Atacama Large Millimeter/submillimeter Array, researchers found that the comet’s chemistry points to an origin in a cold, metal-poor environment unlike the region that formed Solar System comets.

3I/ATLAS is only the third confirmed interstellar object and the second known to show comet-like activity. As it travelled through the inner Solar System, heat from the Sun caused ancient ices preserved from its home system to sublimate, releasing gases into a surrounding coma. This gave astronomers a rare opportunity to study material formed around another star.

The team focused on isotope ratios in water, carbon dioxide and carbon monoxide. Isotopes act like chemical fingerprints because different environments leave different signatures. JWST’s NIRSpec instrument revealed unusually high carbon isotope ratios in CO3 and CO2 along with a water deuterium-to-hydrogen ratio more than an order of magnitude higher than those measured in known Solar System comets. These results suggest that 3I/ATLAS formed from material belonging to an earlier, less chemically evolved stage of the Galaxy. Over time, generations of stars enrich interstellar gas with heavier elements, including carbon-13. A high ¹²C/¹³C ratio therefore points to formation in an old, metal-poor environment.
The water chemistry tells a similar story. The extreme D/H ratio suggests that much of the comet’s water ice formed at very low temperatures and avoided later heating or reprocessing in a young planetary disk.

Although its exact birthplace cannot be traced, 3I/ATLAS preserves a chemical record from another planetary system. Future surveys and missions may reveal whether such ancient interstellar messengers are rare or common.

For more details, read the full article by SETI Institute.