The interstellar comet 3I/ATLAS, only the third such object ever detected, continues to astonish scientists as it journeys through our solar system. New data reveal it is venting water into space at a prodigious rate far from the Sun, suggesting a composition and behavior unlike any comet originating from our own cosmic neighborhood.
A Cosmic Firehose in the Deep Freeze
According to a study published in The Astrophysical Journal Letters, researchers at Auburn University used NASA’s Neil Gehrels Swift Observatory to detect hydroxyl (OH) molecules—a telltale signature of water—in the comet’s coma. The finding itself confirms that the building blocks of life’s chemistry are not unique to our solar system.
The true surprise, however, was the comet’s location and activity. 3I/ATLAS was observed releasing water at a staggering rate of 40 kilograms per second, more than three times the distance to the Sun. At this distance, temperatures are typically too low for such vigorous ice sublimation. The team likened the flow to that of a “hydrant at maximum power.”
Anomalous Theories and Scientific Scrutiny
While the prevailing scientific view is that 3I/ATLAS is a comet, its unusual behavior has prompted some researchers, such as Harvard astronomer Avi Loeb, to call for considering all possibilities. Loeb has publicly speculated that if the object were not natural, it could theoretically release miniature probes to study planets in our solar system, which might even self-replicate to spread more widely. This highly speculative theory is presented as a thought experiment to encourage open-minded analysis of the object’s anomalies, rather than a concluded fact.
An Anomalous Structure from a Foreign Star
This premature outgassing suggests 3I/ATLAS has a complex internal structure. One leading hypothesis is that the comet is so fragile that small ice fragments are breaking off its nucleus. These smaller ice particles have a larger surface area and can vaporize more easily in sunlight, creating the massive cloud of gas detected from Earth.
“Every interstellar comet so far has been a surprise,” said Zexi Xing, an Auburn University researcher and co-author of the discovery. “‘Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS is giving up water at a distance where we didn’t expect it. Each one is rewriting what we thought we knew.”
A Timeline of Intense Scrutiny
The comet, which safely passed Mars in early October, is now racing toward its closest approach to the Sun (perihelion) on October 30. Scientists are watching closely, as comets often disintegrate during this stressful, heated passage.
If it survives, 3I/ATLAS will make its closest approach to Earth in early December, remaining a safe 270 million kilometers away. Meanwhile, the European Space Agency has already captured images with its ExoMars orbiter. It plans to re-task its Jupiter Icy Moons Explorer (JUICE) in November to conduct a detailed study. Data from this observation is expected in early 2026.
As Dennis Bodewits, an Auburn University physicist who collaborated on the research, stated, “When we detect water from an interstellar comet, we’re reading a note from another planetary system.” 3I/ATLAS is that note, and scientists are only just beginning to decipher its message.
