A paper from a SETI (search for extraterrestrial intelligence) Institute scientist has directly addressed claims that interstellar comet 3I/ATLAS is an alien spacecraft.
On July 1, 2025, the Asteroid Terrestrial-impact Last Alert System (ATLAS) detected an object moving through the Solar System on an escape trajectory. Follow-up observations soon confirmed that we were looking at our third interstellar visitor, after ʻOumuamua and 2I/Borisov, although it looks quite different from the previous two. It’s an interesting object, perhaps from an earlier age of the universe and a different part of the galaxy, and even spacecraft around Mars and Jupiter are getting in on the action observing it.
There have been a few suggestions – although not from the majority of scientists – that the object could not be natural at all. Soon after the object was discovered, and before we could take a proper look at it, Harvard theoretical physicist, cosmologist, and astronomer Avi Loeb suggested in a paper that it could be an interstellar probe sent by an intelligent species, potentially with the goal of destroying Earth.
In the first paper, which he states in an accompanying blog post is largely a “pedagogical exercise” and “fun to explore, irrespective of its likely validity”, he suggested that the object could be hostile, as outlined in the “Dark Forest” hypothesis. In short (though you should read the book on which it is based, you will not regret it), given the finite resources in the universe, and our lack of knowledge of any other civilization’s intent, any lifeform may want to pre-emptively attack any other form of life they discover, before it becomes a threat to their own civilization. According to Loeb’s paper, the object could be here for that purpose.
“The low retrograde tilt of 3I/ATLAS’s orbital plane to the ecliptic offers various benefits to an Extra-terrestrial Intelligence (ETI), since it allows the object access to our planet with relative impunity,” Loeb, Adam Hibberd, and Adam Crowl write in that paper.
“The eclipse by the Sun from Earth of 3I/ATLAS at perihelion, would allow it to conduct a clandestine reverse Solar Oberth Manoeuvre, an optimal high-thrust strategy for interstellar spacecraft to brake and stay bound to the Sun. An optimal intercept of Earth would entail an arrival in late November/early December of 2025, and also, a non-gravitational acceleration of ∼ 5.9 × 10–5 au day-2, normalized at 1 au from the Sun, would indicate an intent to intercept the planet Jupiter, not far off its path, and a strategy to rendezvous with it after perihelion.”
Extraordinary claims require extraordinary evidence, and Loeb did not provide this, instead arguing that given the potential consequences of a dark forest strike (Earth goes kablooey), we should consider it, and any planetary defense measures we could take if it were the case.
While speculation like this is enjoyable in a sci-fi context, it has been less than helpful for more conspiracy-minded citizens of Earth. As well as people out there who believe an alien spacecraft is going to approach Earth in late November or early December (per Loeb’s suggestion), there are also people who believe that we are being told a spacecraft is approaching as a cover-up for something else. People are getting real weird with it.
In the paper addressing these claims, which has not yet been peer reviewed, SETI scientist and senior lecturer at the Geoscience Department of Universiti Teknologi Petronas, AKM Eahsanul Haque, outlines why it is likely a natural object.
“Loeb et al. found that the retrograde orbital plane of 3I/ATLAS is quite near to 129the ecliptic, with a 0.2% likelihood that this alignment is not just a coincidence,” Haque writes, adding that the alignment is not impossible for interstellar objects, even if it is statistically rare.
“The galactic disk, which is where most stars are, is nearly in line with the solar system’s ecliptic plane. It is plausible that ISOs that are thrown out of other systems may naturally follow paths that are similar to these.”
“The hyperbolic trajectory, which has an eccentricity of around 6.1, and the high speed of about 58 kilometers per second 134are both consistent with gravitational ejection from a distant star system, according to the measurements 135made in 1I/’Oumuamua and 2I/Borisov. Also, it is important to note that the low likelihood of close encounters with Venus, Mars, and Jupiter, which is about 0.005%, is not only for man-made objects. Natural comets can also have similar dynamics because of changes in gravity.”
Other papers, of course, treat it as an interstellar comet, but do not address these alien technology claims specifically. Loeb and colleagues flagged up a lack of identifiable chemicals as evidence that the comet could be artificial, according to Haque, but comparing the spectral slope with D-Type asteroids and interstellar comet 2I/Borisov, he finds they demonstrate consistency with these other natural objects.
In Loeb’s initial paper and blog post, he states that “detection of a non-gravitational acceleration could also indicate an intent to intercept Jupiter, not far off the path of 3I/ATLAS, and a strategy to rendezvous with it after perihelion.” 2I/Borisov underwent a little non-gravitational acceleration, meaning a change of speed that was not caused by gravitational interactions alone, which astronomers put down to outgassing.
“Seligman et al. also found a slight change in the light curve over about four days, showing that the structure is stable and there is no evidence of acceleration beyond what gravity would cause,” Haque explains. “This differs from the results of 1I/‘Oumuamua, which showed a small, non-gravitational acceleration thought to be caused by outgassing. The fact that 3I/ATLAS did not display such acceleration is a strong argument against the idea of artificial propulsion.”
Since that first paper, Loeb has claimed that a lack of non-gravitational acceleration observed so far could be a sign that there is a “major anomaly” with its mass, and again that the explanation could be aliens.
“The mass of 3I/ATLAS scales with its diameter cubed. If the nucleus diameter of 3I/ATLAS will be found to be larger than 5 kilometers in the HiRISE image, then an origin associated with the interstellar mass reservoir of rocky material will be untenable,” he wrote in a blog post. “An alternative technological origin could explain the rare alignment of the trajectory of 3I/ATLAS with the ecliptic plane (having a random chance of 1 in 500, as discussed here), and the detection of nickel without iron — as found in industrially-manufactured alloys.”
In short; if it accelerates it might be aliens, if it doesn’t accelerate it might be aliens. While alien spacecraft are an undeniably fun topic to talk about, scientists have a much more likely explanation for the object, which is backed up by the evidence. It is a comet.
“It looks like a comet. It does comet things. It very, very strongly resembles, in just about every way, the comets that we know,” Tom Statler, NASA’s lead scientist for Solar System small bodies, said to The Guardian about such claims. “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.”
Based on its trajectory, spectra, and comet-like properties, Haque suggests that it could be “a lithified clastic fragment from an exoplanetary sedimentary basin”. For his own part, Loeb has moved from saying that the idea is purely a teaching exercise, to placing pretty high odds that the object is an alien spacecraft.
“As of now, I assign a 30–40% likelihood that 3I/ATLAS does not have a fully natural origin, based on its seven anomalies that I listed here. This low-probability scenario includes the possibility of a black swan event akin to a Trojan Horse, where a technological object masquerades as a natural comet,” he writes in a new post, adding that his percentages are likely to shift as we get more information on the object.
More information on the object is highly-anticipated by other astronomers too, not because it might be aliens, but because it is an interesting comet from another part of the galaxy, which could operate as a 10-billion-year-old time capsule from an earlier age of the universe. Surely that’s enough?
The paper is posted to the preprint server Earth ArXiv.
Source Link: SETI Paper Responds To Claims Interstellar Object 3I/ATLAS Might Be An Alien Spacecraft
