3I/ATLAS Radio Silence: SETI Institute Shuts Down Alien Signal Myths After Flyby

On Dec. 19, 2025, 3I/ATLAS flew by Earth and did more than just give astronomers something to look at; it brought a piece of a far-off, alien world into our backyard. This cosmic vagabond moves at an incredible 130,000 miles per hour and is only the third interstellar object ever confirmed to have visited our solar system.

3I/ATLAS is a true outsider, unlike the comets that orbit our sun. It was probably born more than seven billion years ago in the galactic thick disc, making it older than the Earth itself. It moves much faster than 'Oumuamua and Borisov, and its path is so 'hyperbolic' that it looks almost straight to the naked eye.

The comet was not dangerous because it was still 168 million miles away, but its flyby sparked an unprecedented international effort to figure out its secrets. Every eye in the sky was on this visitor from the stars, from the surface of Mars to the deep reaches of the Jupiter-bound JUICE probe.

Decoding the Chemistry of 3I/ATLAS

What makes 3I/ATLAS so scientifically delicious is its status as a time capsule. Because it formed around a different star — possibly arriving from the direction of Sagittarius — its chemical makeup offers a rare snapshot of how other planetary systems are built. As it zipped through the inner solar system, NASA's Europa Clipper used its ultraviolet spectrograph to sniff the gases in the comet's coma, while the Parker Solar Probe executed a daring roll to capture images between October and November, even as the Sun's glare blinded Earth-based telescopes.

Observations from the James Webb Space Telescope further revealed a nucleus unusually rich in carbon dioxide, spewing water vapour at a rate of 40 kilograms per second — akin to a firehose at full blast.

The European Space Agency's JUICE mission also managed a 'sneak peek' during its journey to the Jovian moons. Although full high-resolution data won't arrive until February 2026 — owing to the probe using its high-gain antenna as a temporary heat shield — initial images have already revealed a classic 'fuzzball' appearance with two distinct tails: one of plasma and one of dust.

Crucially, astronomers also detected a mysterious 'anti-tail' — a sunward-pointing jet that has defied simple perspective-based explanations. These observations are critical; by comparing 3I/ATLAS to our local comets, scientists can determine if the building blocks of life are universal or unique to our own corner of the galaxy.

Why 3I/ATLAS Stays Grounded in Science

As with any interstellar visitor, the arrival of 3I/ATLAS was accompanied by a predictable wave of 'technosignature' theories. Rumours of artificial radio signals and 'unnatural' course corrections set the internet ablaze. However, the Breakthrough Listen project, employing the massive Green Bank Telescope and the MeerKAT array, conducted an exhaustive search for artificial emissions.

On Dec. 18, just 24 hours before its closest approach, the Green Bank Telescope scanned frequencies from 1 to 12 GHz. Their conclusion was definitive: there is no evidence of alien technology, with sensitivities capable of detecting a signal as weak as a single mobile phone.

Instead of radio broadcasts, telescopes found hydroxyl signatures — the fingerprint of water molecules being ripped apart by solar radiation. In a world-first for an interstellar comet, the object was also imaged in X-rays by XRISM and XMM-Newton.

These images showed a haunting, faint glow stretching for thousands of kilometres, caused by solar wind ions slamming into the comet's gases. NASA has confirmed that any slight deviations in its path are entirely consistent with 'outgassing' — the natural thrust created as ice turns to gas — rather than an artificial engine.

Though it is now racing away from Earth, the journey of 3I/ATLAS is far from over. It is scheduled for a close encounter with Jupiter in March 2026, passing within 33 million miles of the giant planet. By the mid-2030s, it will have crossed the final frontier of our solar system, bound for the darkness of interstellar space once more. For the scientists left behind, the data gathered during this brief visit will provide a roadmap for the next time an alien messenger comes calling.

The short time that 3I/ATLAS spent in our inner solar system is a strong reminder of how much more there is to learn beyond our cosmic horizon. The object is now speeding towards its March 2026 meeting with Jupiter, but the mountains of data it leaves behind will keep scientists busy for years, improving our understanding of the universe's oldest building blocks. As we get ready for the next interstellar messenger, it's clear that we've never been better at working together on scientific projects around the world.