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One might joke that 3I\/ATLAS is a spaceship watching us from a safe distance like the Orville<\/em> watching us from a distance, or maybe it\u2019s the ship of an alien coming to attack us like in the Predator<\/em>.<\/p>\nA paper co-authored by Avi Loeb along with Adam Hibberd and Adam Crowl from the Initiative for Interstellar Studies in London, UK, explores this very hypothesis.<\/p>\n
The paper explores the possibility that 3I\/ATLAS could provide evidence to support the dark forest hypothesis. The hypothesis which was popularized by Cixin Liu\u2019s science fiction novel The Dark Forest<\/em> proposes that our cosmic neighborhood is dangerous, filled with intelligent civilizations that are hostile and silent to avoid detection by potential predators.<\/p>\nIn this context, the silence in searches for radio signals by the SETI community is not caused by the lack of extraterrestrial intelligent civilizations, but is instead a consequence of them fearing mutual destruction.<\/p>\n
3I\/ATLAS, discovered on July 1, is the third confirmed interstellar object after 1I\/\u2019Oumuamua (2017) and 2I\/Borisov (2019).<\/p>\n<\/noscript>This animation shows the observations of comet 3I\/ATLAS when it was discovered on July 1, 2025. The NASA-funded ATLAS survey telescope in Chile first reported that the comet originated from interstellar space. Credit: ATLAS\/University of Hawaii\/NASA<\/figcaption><\/figure>\nUnlike typical asteroids or comets, 3I\/ATLAS displays an unusual combination of features:<\/p>\n
Retrograde yet ecliptic orbital plane<\/strong>: With a tilt of 175.1\u00b0, its path lies nearly flat in the solar system\u2019s plane but travels in the opposite direction\u2014a configuration with a probability of around 0.2%.<\/p>\nUnnatural size<\/strong>: Based on its brightness and assuming a low albedo (reflectivity), 3I\/ATLAS is estimated to be aeound 20 km (12.4 miles) in diameter. This makes it over 100 times bigger than 1I\/\u2019Oumuamua and vastly larger than what models predict for interstellar debris of this kind.<\/p>\nLack of cometary outgassing<\/strong>: Despite its comet-like designation, there are no signs of a coma or tail\u2014raising questions about its propulsion or material makeup. Interstellar comets are expected to outgas when nearing the Sun, as 2I\/Borisov did. The absence of outgassing raises the possibility that the object is either inactive (which is rare near the Sun) or not natural at all.<\/p>\nStriking planetary flybys<\/strong>: 3I\/ATLAS is synchronized to approach unusually close to Venus (0.65 AU \u2014 1 AI is the Earth-Sun separation), Mars (0.19 AU) and Jupiter (0.36 AU), with a cumulative probability of 0.005% relative to orbits with the same orbital parameters but a random arrival time.<\/p>\nSolar eclipse at perihelion<\/strong>: On October 29, 2025, 3I\/ATLAS will be hidden behind the Sun from Earth\u2019s view\u2014a perfect opportunity for a covert reverse Solar Oberth maneuver. <\/p>\nThe optimal point for a reverse Solar\u00a0Oberth maneuver\u00a0to become bound to the Sun is at perihelion. In an\u00a0Oberth maneuver, the thrust of a spacecraft is applied at its maximum orbital speed, namely at periapsis, to maximize the resulting change in kinetic energy.<\/p>\n
This applies both to accelerating to achieve Solar System escape, or alternatively to slow down from a high speed (a `reverse Oberth maneuver\u2019) in order to break, stay bound to the Sun and potentially visit a planet like Earth. It is this optimal breaking point for 3I\/ATLAS that is obscured from our view by the Sun.<\/p>\n
Incoming direction made early detection difficult<\/strong>: The direction from where 3I\/ATLAS is coming is oriented towards the bright Milky-Way center, where crowding by background stars made its detection difficult prior to July 2025. If astronomers were to detect 3I\/ATLAS more than a year earlier, then we would have had an opportunity to launch a spacecraft that could have intercepted 3I\/ATLAS along its path. By now, such an interception is not feasible with chemical rockets.<\/p>\nLow \u2206V required for planetary intercepts<\/strong>: The \u2206V (change in velocity) required for 3I\/ATLAS to intercept Mars, Venus, or Jupiter is unusually low. It is less than 5 km\/s (3 mph) to reach Mars or Venus until July 2025 and less 5 km\/s (3 mph) for Jupiter in November 2025. A \u2206V of 5 km\/s (3 mph) is comparable to that of intercontinental ballistic missiles, making such missions feasible with conventional propulsion.<\/p>\nEarth, however, requires a higher \u2206V \u2014 possibly why 3I\/ATLAS stays away initially. The overall probability of all 3 planets aligning in this is around 0.005%.<\/p>\nDiagram shows the trajectory of interstellar comet 3I\/ATLAS as it passes through the solar system. It will make its closest approach to the Sun in October. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\nA testable theory<\/h2>\n The authors stress that their theory is falsifiable. Should 3I\/ATLAS pass through the solar system without performing unexpected maneuvers \u2014 particularly between November 21 and December 5, 2025 \u2014 the hypothesis would likely be debunked. But if anomalous accelerations or sudden trajectory shifts are observed, the debate could escalate dramatically.<\/p>\n
\u201cA visitor to Earth around the end of November to the beginning of December 2025, whatever form that might take, would clearly support our supposition,\u201d the paper concludes.<\/p>\n
What if it\u2019s natural<\/h2>\n While the authors admit that a natural explanation \u2014 such as a dormant comet or large asteroid \u2014 is more probable, each of those interpretations faces its own difficulties. The apparent size of the object makes it an extreme outlier among known interstellar visitors, and the absence of typical cometary activity raises questions about its physical composition.<\/p>\n
Even if the object turns out to be natural, the calculations and simulations presented offer valuable insights for future interstellar object encounters, especially as the Vera C. Rubin Observatory is expected to detect many more in the coming decade.<\/p>\n
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