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The cosmos is often viewed as a silent, static tapestry, yet recent weeks have reminded us that our solar system is a bustling highway for high-speed traffic. While most of these visitors are understood as natural leftovers from planetary formation, one object has reignited a familiar dispute between mainstream astronomy and those searching for signs of intelligent life.
As interstellar comet 3I/ATLAS continues its one-time flyby, a fierce debate has erupted. Harvard physicist Avi Loeb has warned that such an object could be a “serial killer” alien probe, citing unusual chemical signatures. NASA, however, has pushed back hard, stating there is “overwhelming evidence” the visitor is a natural comet.
The Close Encounter With A High-Speed Interstellar Traveller
On 19 December, the object designated 3I/ATLAS made its closest approach to Earth. The encounter occurred at approximately 6:00 UK time, though ‘close’ is a relative term in astrophysics. The object remained a safe distance away, skimming past at roughly 270 million kilometres (168 million miles).
However, it was not the proximity that raised eyebrows, but the sheer velocity. Hurtling through the void at an estimated 153,000 mph, 3I/ATLAS is moving fast enough to be consistent with an interstellar origin rather than a typical solar system orbit.
Why Unusual Iron Levels Are Fuelling Artificial Origin Theories
Leading the charge for the extraterrestrial hypothesis is Avi Loeb, a physicist from Harvard University who is known for controversial ideas about unusual objects in space. Loeb has argued that reported measurements of the object’s coma—the fuzzy envelope of gas and dust around the nucleus—raise questions worth investigating, particularly claims involving nickel and iron atoms.
In a blog post published in October, Loeb noted that at the distances where such objects are observed, temperatures are generally expected to be too low to vaporise certain grains that contain heavy elements easily. ‘At the distances at which comets are observed, the temperature is far too low to vaporise silicate, sulphide, and metallic grains that contain nickel and iron atoms,’ Loeb wrote.
Loeb illustrated his broader uncertainty about interstellar visitors with a dramatic analogy in comments to Sky News: ‘Alien technology is a potential threat because when you go on a blind date of interstellar proportions, you never know whether you have a friendly visitor as your dating partner or a serial killer.’
🚨 Interstellar Visitor: 3I/ATLAS — Refined High-Resolution Observation (Dec 26)
Images:https://t.co/9mgMBykWLd
A refined deep-sky image captured on December 26, 2025 reveals 3I/ATLAS, an interstellar comet passing through our solar system — only the third confirmed object known… pic.twitter.com/laZe4Pzfec— SpaceTracker.space (@Ammar1176708) December 27, 2025
NASA: ‘Overwhelming Evidence’ Points to Natural Origins
Despite the captivating allure of alien theories, the institutional consensus stands firm. NASA has said there is ‘overwhelming evidence’ the visitor is natural, and agency scientists maintain that the object’s overall behaviour is consistent with a comet.
‘It looks like a comet. It does commit things. It very, very strongly resembles, in just about every way, the comets that we know,’ said Tom Statler, a lead scientist at the agency. He acknowledged that 3I/ATLAS may have some properties that differ from the most familiar solar system comets, but argued that those differences do not require an artificial explanation. ‘The evidence is overwhelmingly pointing to this object being a natural body. It’s a comet,’ he concluded.
The Object’s Journey Toward the Outer Solar System
Regardless of whether it proves to be an unusual natural comet or simply a fairly typical one from another star system, 3I/ATLAS is now leaving us behind. Having completed its flyby of Earth, it is racing toward the outer edges of our system. Trajectory models indicate it is due to pass Jupiter in early 2026.
Its exit will continue for years. Current trajectory models indicate that the object will clear the orbital distances of Saturn, Uranus, and Neptune by 2028. Following this transit, it will remain on a hyperbolic escape trajectory, eventually dropping below the detection threshold of our instruments as it recedes into the interstellar medium.
