Interstellar Comet Discovery and Water Detection

In an exciting scientific discovery, scientists have detected an interstellar comet named 3I/ATLAS releasing large amounts of water, offering a rare opportunity to study the astrochemistry of distant planetary systems. This discovery was made using NASA’s Neil Gehrels Swift Observatory.

Swift Observatory and Water Detection

For the first time, scientists using the Neil Gehrels Swift Observatory have identified the chemical signature of water emitted from the interstellar comet 3I/ATLAS. This comet is the third known object to originate from another star system and be observed passing near our solar system.

Water is considered a universal standard in comet science, used as a baseline to measure how sunlight affects comet activity and the release of other gases. Detecting water in an interstellar comet allows scientists to directly compare 3I/ATLAS with native comets in our solar system.

Unexpected Distance Observation

3I/ATLAS was observed by the Swift Observatory in July and August 2025, while it was about 2.9 times the distance from the Earth to the Sun, far from the region where water ice typically sublimates.

Under these conditions, Swift managed to detect a faint ultraviolet glow of the hydroxyl molecule (OH), a product of water molecule dissociation by sunlight. Scientists noted that the comet was losing water at a rate of 40 kilograms per second, comparable to the force of water being pumped through a fire hose.

Unexpected Activity

Studies suggest that the high activity level in 3I/ATLAS may not be due to its solid surface, but rather the icy debris surrounding it. Near-infrared observations revealed chunks of ice floating in the nebula around the nucleus. Once exposed to sunlight, these chunks heat up and act as small steam vents in space, releasing water vapor even though the comet itself remains too cold for the ice to sublimate directly.

Surprising Interstellar Comets

These studies confirm that every interstellar comet so far has been a surprise; ‘Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS shows water release at a distance where it was not expected. This reshapes our understanding of how planets and comets form around stars.

Conclusion

The discovery of water in comet 3I/ATLAS is a significant step in studying interstellar comets. By observing this comet, scientists can learn more about how planetary systems form elsewhere in the universe. This discovery paves the way for further research into the chemical components of life and their impact on outer space, providing insights into astronomical processes in unfamiliar environments.