Key points: MeerKAT recorded the first radio emission linked to interstellar comet 3I/ATLAS, and analysis shows the signal is absorption from hydroxyl (OH) radicals in the coma, produced when sunlight breaks apart water released by outgassing. The observation confirms earlier NASA reports of strong water jets and supports a natural-comet explanation. Speculative claims that the object is artificial lack supporting evidence, and a related object (C/2025 V1 Borisov) was also judged to be a normal comet.
MeerKAT Detects Radio Signal from Interstellar Comet 3I/ATLAS — It's Natural OH Emission, Not a Message from Aliens
Key points: MeerKAT recorded the first radio emission linked to interstellar comet 3I/ATLAS, and analysis shows the signal is absorption from hydroxyl (OH) radicals in the coma, produced when sunlight breaks apart water released by outgassing. The observation confirms earlier NASA reports of strong water jets and supports a natural-comet explanation. Speculative claims that the object is artificial lack supporting evidence, and a related object (C/2025 V1 Borisov) was also judged to be a normal comet.
04:39 AM, 11/12/2025Science
Radio detection explained: natural comet chemistry, not technology
Astronomers using South Africa's MeerKAT radio telescope have recorded the first radio emission associated with the interstellar comet 3I/ATLAS as it passed near the midpoint of its one-way trip through the solar system. While some speculation framed the detection as potential evidence of extraterrestrial technology, detailed analysis shows the signal is consistent with absorption from hydroxyl radicals (OH) in the comet's coma — a well-known byproduct of water being broken down by sunlight.
What was detected and why it matters
The radio features were first observed on Oct. 24, shortly after 3I/ATLAS briefly went behind the Sun during its perihelion passage (closest approach to the Sun) on Oct. 29. The spectral signatures match OH absorption lines produced when water molecules, released from the nucleus by outgassing, are photodissociated by solar radiation. This provides independent confirmation of the strong water activity that NASA instruments also reported earlier in October.
Separating science from speculation
Since the object's discovery, a small group of researchers — including Harvard astrophysicist Avi Loeb — have proposed speculative ideas that 3I/ATLAS might be artificial. Those suggestions drew public attention but have not been supported by rigorous evidence. The MeerKAT observations strengthen the natural-comet explanation: hydroxyl-radical signatures are a routine outcome of cometary water loss and sunlight-driven chemistry, not engineered transmissions.
Other observations and context
3I/ATLAS has shown several unusual, but explainable, behaviors: a transient brightening and color change around perihelion, a temporary apparent loss of its tail that observers later clarified, a highly irradiated surface, and an elevated carbon-dioxide signature. The wider astronomical community has offered natural explanations for these traits, and most experts consider 3I/ATLAS a natural interstellar comet — possibly an ancient object ejected from another star system billions of years ago.
Related developments
In a related development, rumors that a separate nearby object was a probe launched by 3I/ATLAS were quickly dismissed. The recently observed body, reported as C/2025 V1 (Borisov), passed near Earth on Nov. 11 and was judged to be a typical solar-system comet. Likewise, claims that 3I/ATLAS had exploded from excessive mass loss have been refuted by subsequent observations.
Bottom line: The MeerKAT radio detection reinforces the interpretation that 3I/ATLAS is an active, water-rich comet undergoing photodissociation — not an alien transmitter.