Avi Loeb, Harvard astrophysicist, says massive interstellar object plowing through space toward Mars

Astronomers have been tracking a fast-moving interstellar object called 3I/ATLAS for over two months. The unusual visitor is hurtling toward Mars and could be far more massive than first thought, with some researchers even suggesting it might be a piece of alien technology.

A massive comet or something more?

3I/ATLAS is generally considered a comet but contains unusually high levels of carbon dioxide. Harvard astrophysicist Avi Loeb, who has studied the object in detail, estimates it has a mass of at least 33 billion tons, which would mean its solid-density nucleus is larger than 3.1 miles across.

If confirmed, this would make 3I/ATLAS three to five orders of magnitude more massive than the previous two interstellar objects ever detected (1I/‘Oumuamua in 2017 and 2I/Borisov in 2019).

NASA may get a closer look

Loeb explains that NASA’s HiRISE camera on the Mars Reconnaissance Orbiter is likely to be used to study the object. Observations could refine size estimates and help determine whether 3I/ATLAS is “an unusually massive comet with an unusual chemical composition on an unusually rare trajectory or alien technology.”

Trajectory hints at interstellar origin

3I/ATLAS’ unusually rare trajectory is a key sign that it comes from outside our solar system. The object is expected to pass just inside Mars’ orbit by the end of October, while also passing near Jupiter and Venus. According to NASA, it poses no threat to Earth, remaining at least 170 million miles away.

No observations will be possible from late October through early December 2025, as the object will pass too close to the Sun, delaying further updates.

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