What if 3I/ATLAS were an alien spacecraft? Avi Loeb raises the hypothesis
A Harvard paper analyzes, as an exercise, whether the interstellar visitor could be hostile.
A paper co-signed by Avi Loeb asks whether the third known interstellar object could be alien technology. Its own authors call it a pedagogical exercise.
3I/ATLAS was discovered on July 1, 2025 by the ATLAS survey and is the third interstellar visitor detected, after 'Oumuamua and Borisov. Adam Hibberd and Adam Crowl, of the Initiative for Interstellar Studies, together with Harvard's Loeb, analyzed its trajectory and proposed a testable hypothesis: that it is a technological artifact.
They list oddities: its orbit is barely tilted relative to the plane of the planets, although it is retrograde; it passes surprisingly close to Venus, Mars and Jupiter, with an estimated probability below 0.005%; and at perihelion, on October 29, 2025, it was hidden behind the Sun as seen from Earth. They also propose tests, such as detecting non-gravitational accelerations.
However, the text itself acknowledges that these coincidences may be chance, that the human mind tends to see patterns, and that with only three interstellar objects it is hard to draw conclusions. Its conclusion is clear: 3I/ATLAS is most likely a natural object, probably a comet.
The paper is a preprint on arXiv, not peer reviewed. Its predicted close passes were Mars on October 3, 2025, Venus on November 3, 2025 and Jupiter on March 16, 2026.
Key facts
- Discovered on July 1, 2025.
- Estimated probability of its close pass by three planets: ≲0.005%.
- Perihelion on October 29, 2025, at 1.35 AU from the Sun.
- Later radio searches found no artificial signals.
The calculations can be applied to future interstellar objects detected by the Vera C. Rubin Observatory.
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