3I/ATLAS to Make Closest Approach to Earth — Avi Loeb Suggests Possible Technological Origin

Professor Avi Loeb, a Harvard astrophysicist known for reigniting academic interest in interstellar visitors, has once again made headlines with his latest statements on 3I/ATLAS — the third known interstellar object to enter our Solar System.

In a recent interview, Loeb revealed that NASA had not provided him with HiRISE images of 3I/ATLAS as it passed close to Mars. The high-resolution camera aboard the Mars Reconnaissance Orbiter (MRO) could have captured valuable data about the object’s structure. Nevertheless, Loeb remains optimistic, noting that the object will soon make its closest approach to Earth.

In his latest Medium post, Loeb wrote:

“On December 19, 2025, 3I/ATLAS will arrive closest to Earth at a separation of 269 million kilometers, when hundreds of ground-based telescopes as well as the Hubble and Webb space telescopes will have the best opportunity to observe it.”

He added that:

“Between November 27, 2025, and January 27, 2026, 3I/ATLAS will be monitored by the International Asteroid Warning Network (IAWN) campaign. If the extensive IAWN data will not reveal a massive cloud of gas around 3I/ATLAS, then cometary evaporation would not constitute a natural explanation for its non-gravitational acceleration.”

The physicist also proposed another “litmus test” to determine whether the comet has a natural or artificial origin:

“If we do not observe a massive cloud of gas around 3I/ATLAS in December, then the reported non-gravitational acceleration near perihelion might be regarded as a technological signature of a propulsion system.”

Loeb drew a direct comparison with the first interstellar object ever discovered, 1I/ʻOumuamua, which displayed similar unexplained acceleration:

“A non-detection of an accompanying gas cloud will bring the sensation of déjà vu. The first interstellar object 1I/ʻOumuamua exhibited non-gravitational acceleration without showing any sign of gas or dust around it, even after deep observations by the Spitzer Space Telescope. This led comet experts to define 1I/ʻOumuamua as a dark comet — a comet which does not show a visible tail. Given that a tail is the defining signature of a comet, the notion of a ‘dark comet’ is an oxymoron. A spacecraft with a propulsion system could show a non-gravitational acceleration without cometary evaporation. It could be classified by comet experts as a dark comet in the same way that a cave dweller would classify a cell phone as a rare rock.”

Finally, addressing his critics, Loeb remarked:

“Scientific truth is not decided by a popularity contest but by attention to data—especially when it is anomalous.”

As 3I/ATLAS approaches Earth in December 2025, astronomers worldwide will be watching closely. Whether the object reveals a natural cometary nature or something far more mysterious, it promises to deepen our understanding of interstellar visitors—and perhaps of intelligent life beyond Earth.