Astronomers studying the interstellar visitor 3I/ATLAS have discovered that the comet is unusually rich in alcohol – a chemical clue that could reveal how planets and icy bodies form around other stars.
Using the powerful radio antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, researchers detected extremely strong signals of methanol (CH3OH), a single alcohol molecule, i the cometits expanding gas cloud.
Seam 3I/ATLAS approached the sun and sunlight heated the icy surface, releasing gas and dust, and forming a glowing halo – or coma – around the nucleus, which allowed ALMA to analyze the comet’s chemical composition in detail.
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The measurements show that methanol is far more abundant in relation to hydrogen cyanide than astronomers usually see in comets from our own the solar system. The chemical imbalance suggests that 3I/ATLAS likely formed in a planetary system with very different physical conditions — such as colder temperatures and/or a different chemical inventory — than the one that produced our own comets, according to a statement from the National Radio Astronomy Observatory (NRAO).
“Observing 3I/ATLAS is like taking a fingerprint from another solar system,” Nathan Roth, lead author of the study and a professor at American University, said in the statement. “The details reveal what it’s made of, and it’s full of methanol in a way we don’t usually see in comets in our own solar system.”
Methanol – which is used for industrial purposes here on Earth, as opposed to the potable ethanol – is not rare in space. It forms on the surfaces of icy dust grains in interstellar clouds and is often incorporated into comets during planet formation. But the amount detected in 3I/ATLAS seems unusually high compared to the conditions seen in Solar System comets, making the object a valuable chemical “fingerprint” of another planetary system.
Discovered in July 2025 by the Asteroid Terrestrial-impact Last Alert System, 3I/ATLAS is only the third known object confirmed to have entered the Solar System from interstellar space. The first was ‘Oumuamuadiscovered in 2017, followed in 2019 by 2I/Borisovwhich displayed a more traditional comet-like appearance.
Since the discovery of 3I/ATLAS, telescopes around the world – including The Hubble Space Telescope and that The James Webb Space Telescope — has monitored the comet as it travels through the inner solar system. Images show a diffuse coma and faint dust tail created when sunlight heats the comet’s ice, releasing gas and dust into space.
These outflows also help explain another phenomenon observed around the comet: a huge cloud of gas that glows in X-rays as charged particles from solar wind beat into material escaping from the core. The ALMA observations further revealed that hydrogen cyanide mostly flows directly from the comet’s nucleus, while methanol is released both from the nucleus and from icy grains in coma acts as a miniature micrometer — the first time such detailed outgassing behavior has been mapped in an interstellar object, according to the statement.
The arrival of a new interstellar object has also fueled speculation onlineincluding suggestions that 3I/ATLAS may be of artificial origin. But the growing body of evidence – including its comet-like tail, gas jets and molecular composition – strongly indicates that the object is a naturally icy body.
For astronomers, that’s the real thrill. Objects like 3I/ATLAS act as messengers from other planetary systems, preserving the chemical conditions in which they formed billions of years ago—and offer rare opportunities to study the building blocks of distant worlds without ever leaving our own solar system.
The new study has been submitted for publication and is currently available as a preprint on arXiv.
