This is not the first time that a comet is accusing it of being a spy. However, 3I/ATLAS, which was introduced on July 1, 2025, by the ATLAS telescope in Chile, has already raised a debate like no others of its predecessors ʻOumuamua and 2I/Borisov. This size of interstellar spacecraft, estimated to be 20–40 km in diameter, flew into the solar system at a speed of more than 50 km/s on a hyperbolic orbit, assuring that it originated outside of the Sun. But it is the late-forming coma of the comet, its lingering coma towards the sun, its recently photographed wobbling twin-jet form which has launched it into the speculation about alien engineering.
At first, 3I/ATLAS did not have any coma, but only formed one at the unusually late date after moving past perihelion, November 30, 2025, at 1.4 AU. In the majority of comets, the onset of the sublimation process is earlier, with solar heating forcing the volatile ices to out-gass and out-dust. Researchers have been at a loss to explain the delay and Harvard astrophysicist Avi Loeb has taken advantage of such anomalies to propose the existence of a technological source – perhaps a reconnaissance probe with technology propelled by science-fiction-like propulsion or shielding. Some of his listed anomalies include non‑gravitational acceleration, extremely high variations in brightness as well as having a tail that points towards the Sun instead of away.
Images taken on December 12 and 27 using the Hubble Space Telescope showed a constant double jet 100,000 km long out of the nucleus rotating with the 8-hour rotation period of the comet. The striking “anti-tail” is made by one jet and the less powerful one is in line with previous action experienced in July. According to Loeb, a wobble of approximately 7 degrees about the axis of rotation means the sunward jet must have started forming long before perihelion around the pole that is facing the sun. In physical comet observations in nature this might be attributed to slow venting of the nightside caused by thermal conduction, or jets could be ejected on alternate sides of the nucleus as various volatile storehouses were tapped. In the technological vision of Loeb, the two jets could be used defensively as a shield against the solar wind or debris, or as a jet with a different composition or direction of thrust.
Cometary jets have natural explanations which are provided by their physics. The distance grains (dusts) coming off the sunlit hemisphere have the capability of forming a sunward-facing feature when they are not moved antisolar by radiation pressure, which has been observed in other comets such as C/2014 UN271. Localized vents can outgass to produce collimated flows of up to 1 km/s, which is in agreement with the 1 km/s speeds that Loeb predicts in the event that the jets were actively regulated. The velocity measurements on the spectroscopes in other telescopes such as the Keck and the Very Large Telescope will play a significant role in showing whether the jets are driven solely by volatiles and whether there is any evidence of an engineered thrust.
The mystery is further built up by composition. Nickel was observed without iron in the coma without iron, and this was rarely observed, indicating possible unusual chemical processing, by observations with the Very Large Telescope. In the James Webb Space Telescope, a very high CO 2 /water ratio, one of the highest ever observed in any comet, was measured. The NASA IRTF and Gemini South infrared spectrums reported the presence of large quantities of water ice in combination with organics, silicates and carbonate minerals, and its reflectance spectrum was similar to that of D-type asteroids. In the event of a positive result, the water ice can be pronounced to be seven billion years old, which is older than the solar system itself and provides a pure sample of a protoplanetary disk of another star.
The hyperbolic orbit and velocity of 3I/ATLAS (approximately 130,000 mph when compared to the Sun) is astrodynamically predicted to have wandered the galaxy over eons and may have formed in the thick disk of the galaxy composed of the stars. It came so close on December 19, 2025, that it was within 1.35 AU of Earth, allowing close examination, but not anywhere near the danger of collision. Non-gravitational acceleration has been detected at perihelion, but thermophysical simulations by Florian Neukart demonstrate that the magnitude and direction of conventional outgassing of CO and CO 2 with sub-percent active surface coverage can both be reproduced without exotic propulsion. The discovery of OH absorption in the MeerKAT radio telescope proves the active release of water after perihelion which is a characteristic of natural cometary activity.
The anti-tail, though not the first of its kind, is not out of step with models of morphology of comets. Emitted dusts in the pre-perihelion period may cause a sunward enhancement under conditions of alignment between geometry and particle dynamics, as explained in the classic 1974 article by Z. Sekanina. The persistence of the feature and its alignment with the jet activity in 3I/ATLAS are a feature of the best case study to optimize such models, especially in the special conditions of an interstellar comet.
As 3I/ATLAS approaches the orbit of Jupiter (where it is going to approach closest in March of 2026), scientists hope to obtain high-resolution spectra and list the volatile and dust elements within 3I/ATLAS. Such data will assist in establishing whether the activity after perihelion alters composition, e.g. in 2I/Borisov and whether the velocity profiles of the jets are natural sublimation, or more intentional. To space fans and scientists, the comet itself represents the edge at which the astrophysics borders the exoticism of alien possibility: a rarity, an interstellar messenger, the behavior of which pushes the models, creates controversy and requires the maximum level of testing that contemporary astronomy can offer.
