On July 1, 2025, the Asteroid Terrestrial-Impact Last Alert System (ATLAS) based in Chile identified a new comet entering our solar system, designated as 3I/ATLAS. This marks it as the third interstellar object observed by humanity, following 1I/’Oumuamua in 2017 and 2I/BORISOV in 2019. 3I/ATLAS shares similarities with 2I/BORISOV, particularly its icy composition. However, much about this new visitor remains unknown. Scientists are eager to study 3I/ATLAS since it is expected to exit our solar system by the year’s end, following its current trajectory and speed.
The comet is projected to make its closest approach to the Sun in late October 2025. During this time, solar heating may melt some of its icy surface, potentially creating a prominent tail of vapor and dust. Currently, 3I/ATLAS exhibits a faint coma—an envelope of dust and gas surrounding its nucleus—but this may change as it nears the Sun. Another noteworthy aspect is that the comet will pass through the orbit of Mars, raising questions about what might occur during that transit.
ATLAS, the observatory that first detected 3I/ATLAS, is designed with a defensive purpose, monitoring for comets, asteroids, and other celestial bodies that could collide with Earth. However, NASA has indicated that this interstellar object is unlikely to pose any danger as it will travel well beyond Earth’s orbit.
The ATLAS facility is part of NASA’s early warning initiative, tracking near-Earth objects (NEOs) that could threaten our planet. Utilizing a network of wide-field telescopes operating continuously, ATLAS is equipped to detect both hazardous and scientifically intriguing space objects. The telescopes are strategically located in various observatories worldwide, including South Africa, California, and Chile, ensuring comprehensive coverage of the night sky.
Upon discovering 3I/ATLAS, the initial focus was on determining its trajectory and velocity. Scientists discovered that it is traveling at approximately 137,000 miles per hour (61 km/s) and will come within 1.8 astronomical units (170 million miles or 270 million kilometers) of Earth. NASA has confirmed that 3I/ATLAS poses no threat to our planet.
One of the most captivating aspects of this interstellar visitor is its age. Researchers calculated its trajectory and found that 3I/ATLAS likely originates from a region of the Milky Way older than our solar system, suggesting it could be over 4.6 billion years old. Estimates indicate that it is roughly 7 billion years old, making it the oldest comet observed by humanity.
Intriguingly, some theories speculate that 3I/ATLAS may not be a comet at all, but rather an extraterrestrial probe. Harvard astrophysicist Abraham Loeb, along with colleagues from the Initiative for Interstellar Studies in the UK, suggested this notion, advocating that interstellar objects should be investigated as potential alien technology. This isn’t Loeb’s first foray into such speculation; he previously proposed a similar idea regarding Oumuamua, citing its peculiarities.
At present, there is no evidence supporting the claim that 3I/ATLAS is anything beyond an interstellar comet. Its identification by ATLAS is fortunate, as many similar objects likely pass through or near our solar system without detection. Though theories abound, it remains essential for scientists to observe 3I/ATLAS closely, given its unique nature as an interstellar comet.
