The third interstellar visitor, 3I/ATLAS, is now heading for the sun after its Mars flyby. What does its unusual composition reveal about alien star systems? Expert reports on the fastest object ever recorded.

The unprecedented passage of Comet 3I/ATLAS, only the third confirmed interstellar visitor to our solar system, reached a critical juncture this week, making its closest approach to the planet Mars on October 3, 2025.

As spacecraft and rovers captured once-in-a-lifetime data, the scientific community remains divided over whether the high-speed object is merely a natural cosmic snowball or, as some speculate, an engineered artifact from another civilization.

The comet, discovered by the ATLAS survey in July, is currently accelerating toward its closest point to the Sun (perihelion) later this month, traveling at an astonishing velocity exceeding 130,000 mph.

Mars Missions Capture Historic Close Approach

On Friday, October 3, 3I/ATLAS passed within approximately 18 million miles (29 million kilometers) of Mars. This close flyby was immediately exploited by a fleet of international orbiters, including NASA’s Mars Reconnaissance Orbiter (MRO) and the European Space Agency’s (ESA) Mars Express and ExoMars Trace Gas Orbiter (TGO).

Imaging Data Pending: Mission teams on Earth are currently processing the high-resolution images and spectral data captured by the orbiters, which will provide the closest-ever look at the comet’s nucleus and its outgassing composition. Early reports from citizen scientists analyzing raw data suggest NASA’s Perseverance and Curiosity rovers on the Martian surface may have also caught faint glimpses of the fast-moving “smudge” in the Martian night sky.
Controversial Timing: Ironically, the public release of data from NASA’s instruments could be delayed due to a reported government shutdown, leaving the world reliant on European and amateur observations during this key period.

Size and Composition Fuel the Alien Debate

New data on the comet’s size and trajectory continue to baffle some experts, particularly Harvard astrophysicist Avi Loeb, who has been a vocal proponent of non-natural origins.

A Cosmic Colossus: Latest estimates suggest 3I/ATLAS has a nucleus diameter potentially exceeding 3 miles (5 kilometers) and a mass surpassing 33 billion tons, making it significantly larger than the previous two interstellar objects, ‘Oumuamua and Borisov.
Anomalies: Dr. Loeb and his team point to several “anomalies,” including the object’s unexpectedly large size, its unusual chemical signature (high in nickel relative to iron), and its trajectory alignment, which they argue is too precise to be purely coincidental.

However, the consensus among NASA and ESA scientists remains firm: 3I/ATLAS is a natural interstellar comet. They note that the object is behaving in line with cometary physics, even if its specific chemical makeup is a rare “messenger” from another planetary system.

Safe Journey, Never to Return

Planetary defence experts confirm that the public remains safe. 3I/ATLAS will not approach Earth closer than 170 million miles.

After passing inside the orbit of Mars for perihelion on October 29, the comet will head toward the orbit of Jupiter in March 2026, where ESA’s JUICE mission will continue to monitor it.

Its hyperbolic path confirms that 3I/ATLAS is a fleeting visitor, soon to be ejected from our solar system entirely, taking its secrets, whether natural or technological, back out into the vast gulf of interstellar space.

Follow Europeans24 for more interesting space facts! 3i atlas update