For millions of years, a tiny icy fragment wandered through space, like a sealed bottle drifting across a cosmic ocean. This summer, that "message in a bottle" arrived in our solar system, named 3I/ATLAS, only the third known interstellar comet.
Researchers from Auburn University used NASA's Neil Gehrels Swift Observatory to study it, making a groundbreaking discovery: a faint glow from hydroxyl gas (OH), a chemical sign that water was escaping from the comet.
This marks the first time water-related activity has been detected in an interstellar comet. Normally, telescopes on Earth can't detect such faint ultraviolet light because our atmosphere blocks it.
A "message in a bottle" arrived in our solar system.
Author's summary: Astronomers detect water in interstellar comet 3I/ATLAS.