Astronomers have recently detected a rare and enigmatic interstellar object named 3I/ATLAS speeding through our solar system. Discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile on July 1, 2025, 3I/ATLAS is only the third confirmed interstellar visitor after ‘Oumuamua (2017) and 2I/Borisov (2019).
3I/ATLAS displays characteristics of an active comet, including a cometary coma and tails formed by gas and dust sublimating from its icy nucleus as it warms near the Sun. Observations by the Hubble and James Webb Space Telescopes estimate its nucleus diameter to be under 1 km, though it emits an unusually bright glow with spectral signatures of carbon dioxide, water ice, cyanide, and atomic nickel.
However, Harvard astrophysicist Avi Loeb and colleague Eric Kito have provocatively suggested in a recent paper that the object’s brightness profile, focused orbital path closely aligned with planetary orbits, and “reverse solar Oberth maneuver” hint that 3I/ATLAS could be artificial—possibly an alien probe testing or observing Earth. This hypothesis remains controversial among scientists.
The object’s trajectory will bring it unusually close to Mars, perihelion between Earth and Mars in late October 2025, and later near Jupiter, offering unprecedented observational opportunities using Mars orbiters and advanced telescopes. These observations could confirm if the glow is self-luminous or merely reflected sunlight, helping determine the true nature of this cosmic visitor.
Scientists remain divided, with many considering 3I/ATLAS a comet while others find peculiarities that defy conventional explanations. The coming months are critical for unraveling this mystery and understanding the origins and nature of 3I/ATLAS.