The 'alien comet' is on the way: 3I/ATLAS to make rare Earth pass

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The 'alien comet' is on the way: 3I/ATLAS to make rare Earth pass
Ariana Garcia
Fri, December 12, 2025 at 2:28 PM EST
4 min read



An illustration shows 'Oumuamua. 3I/ATLAS is the latest interstellar comet lighting up the solar system, and it will make its closest approach to Earth on Dec. 19. (Getty Images)


Comet 3I/ATLAS, only the third known object from interstellar space to pass through our solar system, is about to make its closest approach to Earth. On Friday, Dec. 19, it will come within about 170 million miles of the planet while moving on the far side of the Sun. The alignment should give Earth and space-based telescopes one of their best opportunities to study it, and NASA says it poses no threat.

Astronomers have followed 3I/ATLAS since its discovery on July 1. Hubble photographed it on July 21 from 277 million miles away, revealing a teardrop-shaped cloud of dust wrapped around its icy core. The comet stayed visible through September before slipping too close to the Sun to be observed.

In early October, three NASA spacecraft at Mars-MRO, MAVEN, and Perseverance-picked it up again. MRO's HiRISE camera, usually aimed at the Martian surface, captured the clearest view: a tiny, pixel-like puff representing the coma, the dusty envelope created as sunlight warms the nucleus.



Comet 3I/ATLAS as seen through the High Resolution Imaging Science Experiment (HiRISE) aboard the agency's Mars Reconnaissance Orbiter (MRO), during its close pass by Mars on Oct. 3, when it swept within 18 million miles of the planet. (NASA/JPL-Caltech/University of Arizona)


Ongoing observations will help scientists refine estimates of the comet's size and composition and better understand the dust particles in its coma. Current measurements suggest it could span anywhere from 1,444 feet to 3.5 miles.

3I/ATLAS follows two earlier interstellar objects, 1I/'Oumuamua and 2I/Borisov. Unlike 'Oumuamua, which behaved more like a rocky object, 3I/ATLAS displays classic comet activity. Even so, some of its traits have generated debate. Harvard astrophysicist Avi Loeb, who previously raised the possibility that 'Oumuamua might be artificial, has again questioned whether this object could have a technological origin, though most scientists continue to interpret it as a natural comet.

Loeb wrote that comets shed gas and dust when sunlight warms icy pockets on their surfaces, which produces a small push similar to a rocket. He noted that an artificial object could experience similar non-gravitational forces, either through propulsion or by collecting material as it moves through interstellar space, making it appear comet-like in low-resolution images.

"Given these features, it may resemble a comet in unresolved images like the ones we have of 3I/ATLAS," he wrote. "However, a spacecraft could also display artificial lights, release excess heat from its engine or maneuver in unusual ways."



NASA's Hubble Space Telescope reobserved interstellar comet 3I/ATLAS Nov. 30, with its Wide Field Camera 3 instrument. (NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory). Image Processing: J. DePasquale (STScI))


He highlighted several other features he considers unlikely for a natural object, including the comet's trajectory. Loeb wrote that its path is aligned with the plane of the planets to within five degrees, something he calculates as having only a 0.2 percent chance of occurring by accident.

He also pointed to a jet of material directed toward the Sun before and after perihelion, which he calls unusual for familiar comets. He argued that its timing placed it unusually close to Mars, Venus, and Jupiter while keeping it unobservable from Earth at perihelion. He also contends that the object's estimated mass and high speed make it unlikely to be a naturally occurring rock randomly entering the inner solar system.

Scientists will continue studying the comet after its closest approach. "Observations are expected to continue for several more months as 3I/ATLAS heads out of the solar system," NASA noted.

The European Space Agency's JUICE spacecraft also observed 3I/ATLAS last month and saw intense activity as sunlight heated the comet, causing its ices to sublimate. ESA expects most of JUICE's data to arrive in late February.

After passing Earth, 3I/ATLAS will move on toward Jupiter in spring 2026, providing another chance to examine this rare visitor from beyond the solar system.

https://www.yahoo.com/news/articles/alien-comet-way-3i-atlas-192833180.html