The interstellar comet that’s like a cosmic hydrant: 3I/ATLAS is releasing water in unexpected places!
When astronomers pointed their instruments towards 3I/Atlas, they expected to see a frozen rock wandering silently through the void. What they found, however, was a pressurized water source open in space. At three times the distance between Earth and the Sun, the comet was already spewing vapor at a rate of 40 kilograms per second, like a fire hydrant in space. At that distance, the solar heat is too weak to cause the ice to sublimate. And yet, something inside it seems to operate under different laws.
An Interstellar Visitor
3I/Atlas is only the third interstellar object detected in history, after ‘Oumuamua and Borisov. It comes from another stellar system, from an environment that no one knows. Its fleeting passage offers a unique opportunity to observe how comets from other suns are—or were—like.
Researchers were able to detect its chemical signature using NASA’s Neil Gehrels Swift Observatory, a 30-centimeter diameter space telescope that achieves a resolution similar to that of a four-meter mirror outside Earth’s atmosphere. Swift observed an ultraviolet emission of hydroxyl (OH), the unmistakable trace that water is decomposing under the sunlight.
“A structure that puzzles science”
The intensity of the water flow suggests that 3I/Atlas does not have a compact nucleus, but a fragmented structure. Small pieces of ice break off and evaporate upon contact with light, generating a cloud of vapor that envelops the comet. It is a behavior rarely seen even in the most active comets in the Solar System.
For researcher Zexi Xing, a co-author of the study, 3I/Atlas becomes a crucial clue to understanding how worlds are formed. “‘Oumuamua was arid, Borisov was rich in carbon monoxide, and now 3I/Atlas emits water at an unexpected distance. Each one rewrites what we thought we knew about comets and the planets around them.”
“A message from other suns”
In practice, observing an interstellar comet is like receiving a fragment from another stellar system without leaving our own. Every water molecule, every ultraviolet light emission, tells the story of a place that may no longer exist.
And as 3I/Atlas continues its journey, moving away from the influence of the Sun, it leaves behind a subtle yet powerful clue: the certainty that the chemistry of life—and perhaps life itself—could be much more common than we imagine.
