Is comet 3I/ATLAS cosmic ally — or "serial killer"? Harvard scientist weighs in

Harvard astrophysicist Avi Loeb is asking whether the interstellar comet 3I/ATLAS — due to sweep past Earth in two weeks — is a benign visitor or something more ominous. He says the answer may lie in the unusual mix of chemicals streaming from its twin tails.

“There is much more methanol than hydrogen cyanide,” Loeb told The New York Post.

“In principle, methanol is an important agent for the origins of life.” He added, “And on the other hand, the hydrogen cyanide at large concentrations is a poison.”

Fresh images captured by the European Space Agency’s Juice mission show ATLAS venting large clouds of gas after skimming past the Sun, according to IFL Science. In a recent Medium post, Loeb explored how the comet’s chemical emissions — detected in the autumn by the ALMA radio telescope in Chile — may hint at its origins or purpose.

The abundance of methanol is notable, Loeb said, because it is “a building block for amino acids and sugars that are used for organic chemistry of life.” Methanol has previously been observed around young stars and in planet-forming discs, including ones spotted by MERLIN and ALMA in 2006 and 2016, respectively.

However, ATLAS also contains hydrogen sulphide — once used as a chemical weapon during World War I — raising a darker possibility. Loeb joked that “on a blind date with an interstellar visitor, it is prudent to observe the dating partner and decide whether it could have seeded life on Earth” or “whether it represents a serial killer spreading poison”.

For now, the evidence points to a largely harmless interloper. Loeb notes that ATLAS exhibits one of the highest methanol-to-hydrogen-cyanide ratios ever recorded in a comet, suggesting a more “friendly” character. He even speculates that objects like ATLAS may have delivered the raw materials for life early in the solar system’s history. “If the solar system didn’t have the building blocks, it could have gotten them from the visits of objects like 3I/Atlas in the early solar system,” he told The Post.

Loeb has previously proposed that Earth could have been “pollinated” over billions of years by multiple interstellar visitors — including some potentially artificial.

He says the latest findings do not rule out an engineered origin for ATLAS, noting that “fuel that is being consumed ends up producing methanol”, and referring to its “complex jet structure”, which he has likened to possible thrusters.

More clarity may come next year, with the European Space Agency set to publish new Juice data in February 2026. Meanwhile, the James Webb Space Telescope is expected to capture detailed images as ATLAS passes closest on December 19.

By Aghakazim Guliyev