NASA has weighed in on speculation that the newly discovered interstellar object 3I/ATLAS might be an alien spacecraft, an idea popularized by Harvard astronomer Avi Loeb. While Loeb floated the possibility that it could be an extraterrestrial probe with hostile intent, NASA scientists insist that all evidence points to a much simpler explanation: it’s just a comet.
Astronomers first spotted 3I/ATLAS on July 1, 2025, moving through the Solar System at nearly double the speed of earlier interstellar visitors, ‘Oumuamua and Comet Borisov. At an estimated 5.6 kilometers (3.5 miles) across, its nucleus makes it far larger than either of its predecessors. Beyond its size, scientists are intrigued because the object may have originated from an entirely different region of the galaxy, making it potentially older than any known Solar System body.
But intrigue quickly turned into speculation. Soon after the discovery, Loeb suggested the comet might actually be a hostile interstellar probe, citing the “Dark Forest” hypothesis from science fiction literature. On his blog, he argued: “3I/ATLAS achieves perihelion on the opposite side of the Sun relative to Earth. This could be intentional to avoid detailed observations from Earth-based telescopes when the object is brightest or when gadgets are sent to Earth from that hidden vantage point.”
He went further, proposing that the object could perform a “reverse Solar Oberth maneuver” at perihelion, a technique that could, in theory, help it slow down and become bound to the Sun, eventually reaching Earth by late 2025. Loeb’s paper even raised the possibility that defensive measures might be needed, though he admitted they would likely be “futile.”
This isn’t Loeb’s first foray into alien theories. He previously argued that ‘Oumuamua could be a light sail from another civilization, a claim that drew wide attention and criticism within the scientific community.
Despite the hype online, the scientific consensus is firm: 3I/ATLAS is behaving exactly like a comet. Tom Statler, NASA’s lead scientist for Solar System small bodies, dismissed the spacecraft speculation in comments to The Guardian: “It looks like a comet. It does comet things. It very, very strongly resembles, in just about every way, the comets that we know. It has some interesting properties that are a little bit different from our solar system comets, but it behaves like a comet. And so the evidence is overwhelmingly pointing to this object being a natural body. It’s a comet.”
Studies of the object confirm it has a dusty coma and shows no signs of being artificial. While scientists acknowledge its unusual speed and size, these traits still fall within natural expectations for an interstellar comet.
At its closest approach to the Sun, 3I/ATLAS will be hidden from Earth’s direct view, but astronomers will continue tracking it with available instruments. NASA emphasizes that the comet poses no threat to Earth, nor is there evidence of alien technology lurking within it.
