Interstellar comet 3I/ATLAS is leaking water like a ‘fire hose running at full blast,’ new study finds

According to a recent study, a rocky visitor from space is “fire hose running at full blast,” leaking water.

For the first time, researchers have identified the chemical fingerprint of water leaking from interstellar comet 3I/ATLAS, which is only the third known object from another star system to ever be seen traveling through our cosmic neighborhood, using NASA’s Neil Gehrels Swift Observatory.

The standard by which comet scientists measure how sunlight affects a comet’s activity and releases other gases is water. By spotting it in an interstellar visitor, astronomers can directly compare 3I/ATLAS with comets that are part of our solar system, providing a unique window into the chemistry of far-off planetary systems.

In a statement, study co-author Dennis Bodewits, a physics professor at Auburn University, said, “We’re reading a note from another planetary system when we detect water — or even its faint ultraviolet echo, OH — from an interstellar comet.”. It indicates that the components of life’s chemistry are not exclusive to humans. “..”.

“At a distance that caught us off guard.”.

Bodewits and his colleagues used the Swift telescope to observe 3I/ATLAS in July and August 2025, when it was approximately 2.9 times further away from the sun than Earth, well outside the area where water ice normally vaporizes.

“From this distance, Swift detected the faint ultraviolet glow of hydroxyl (OH), which is the result of sunlight breaking down water molecules,” the study says. Astronomers combined over two hours of ultraviolet observations with 40 minutes of visible light exposures to stack dozens of brief, three-minute exposures in order to extract the delicate signal.

The outcome was described in a paper by Sept. 30 in the Astrophysical Journal Letters, revealed that 3I/ATLAS was losing water at a rate of about 40 kilograms per second, which is “about the output of a fire hose running at full blast.”. “.”.

The team calculates that at least 8% of the comet’s surface must be active based on that outflow rate, which is a surprisingly high percentage when compared to the 3–5% usual for comets from our own solar system, the study says.

According to the researchers, icy debris floating around it could be the source of that level of activity rather than its solid surface. Gemini South and NASA’s Infrared Telescope Facility have made near-infrared observations that suggest ice fragments floating in the coma, which is the cloud of gas and dust that surrounds the nucleus. Even though the comet itself is still too cold for its surface ice to sublimate directly, the researchers claim that once these clumps are warmed up by sunlight, they function as tiny steam vents in space, releasing water vapor.

The new study’s lead researcher, Zexi Xing, a postdoctoral researcher at Auburn University in Alabama, said in the same statement, “Every interstellar comet so far has been a surprise.”. Borisov had a lot of carbon monoxide, Oumuamua was dry, and now ATLAS is releasing water at a distance that surprised us. Each one challenges our preconceived notions about how comets and planets form around stars. “,”.

Since then, 3I/ATLAS has slipped out of Swift’s line of sight, but in early October, the European Space Agency’s Mars orbiters caught another glimpse of it as it passed roughly 30 million kilometers away from Mars. The agency stated that it will keep tracking the interstellar visitor and that it intends to target 3I/ATLAS with its Jupiter Icy Moons Explorer (JUICE) in November.

JUICE is expected to have the best view of this action because it will be observing the comet shortly after its closest approach to the sun, when it is most likely to be active, the agency said.

Scientists anticipate receiving JUICE’s comet observations in February 2026 because the spacecraft is now on the sun’s far side and transmitting data using a slower backup antenna.