The ancient interstellar visitor in our Solar System is on a trajectory to encounter a NASA spacecraft in just a few weeks.
The object 3I/ATLAS is expected to pass near NASA’s Europa Clipper and the European Space Agency’s Hera spacecraft between October 25 and November 6.
European researchers released a pre-print study discussing the rendezvous, saying the craft will be ‘immersed within the ion tail of 3I/ATLAS, providing the opportunity to detect the signatures of an interstellar comet’s ion tail.’
One of the most interesting possibilities is encountering the comet’s ion tail, a stream of charged particles extending millions of miles from the coma.
Encounters with ion tails are unusual and valuable because they provide a direct sample of material from beyond our Solar System. Historically, such crossings have been difficult to detect, and many may have gone unnoticed, appearing only as small fluctuations in solar wind and magnetic field measurements.
To predict these potential encounters, researchers use the Tailcatcher program, which calculates the closest approach, or ‘impact parameter’ of a spacecraft to a comet’s ion tail based on solar wind flow.
For 3I/ATLAS, Tailcatcher predicts minimum distances of roughly five million miles.
Researchers noted that even if Europa Clipper cannot measure all components, the mission could reveal the structure and composition of the ion tail, helping scientists understand the properties of interstellar bodies.
As discovery rates of such objects improve, future spacecraft, including ESA’s Comet Interceptor, may be able to encounter interstellar objects at even closer range, opening a new era in the study of visitors from other star systems.
Co-author Samuel Gran, a postdoctoral researcher at the Finnish Meteorological Institute, told Space.com: ‘We have virtually no data on the interior of interstellar comets and the star systems that formed them.
‘Sampling the tail in this way is the closest we can currently get to a direct sample of such an object, and thus a different part of the galaxy.’
NASA’s Europa is traveling to Jupiter’s moon Europa, and the ESA’s Hera is currently in the asteroid belt, traveling to the Didymos-Dimorphos.
Didymos-Dimorphos is a binary asteroid system in the asteroid belt, consisting of a larger primary asteroid, Didymos, which is about 2,500 feet in diameter, and a smaller moonlet, Dimorphos, which orbits Didymos at roughly 0.75 miles and measures about 525 feet (160 meters) across.
The system gained attention when NASA’s DART mission deliberately impacted Dimorphos in September 2022 to test planetary defense by slightly altering its orbit. It serves as an important target for studying asteroid composition, orbital dynamics, and strategies for protecting Earth from potential asteroid impacts.
The study explained that the Europa probe is equipped with instruments to study plasma and a magnetometer, while ESA’s Hera mission cannot measure ions or magnetic fields.
If solar wind conditions are favorable, Europa Clipper will have a rare chance to study material from the tail of an interstellar object, the report added.
While the researchers and NASA have determined 3I/ATLAS is a comet, Harvard professor Avi Loeb believes all data should be considered before a conclusion is made.
He has stated there is a 30 to 40 percent chance the object ‘does not have a fully natural origin,’ noting the possibility it is a ‘Trojan Horse,’ where a technological object masquerades as a comet.
The claim is based on anomalies observed with the object, including a release of specific metals, its trajectory and how it has flipped its jet around twice.
The odd behavior has also led the International Asteroid Warning Network (IAWN) to launch a campaign for further analysis of the object.
IAWN works alongside institutions across the world that detect, track, and study near-Earth objects (NEOs) to assess potential impact threats to Earth.
3I/ATLAS is the first interstellar object ever added to the list, triggering a worldwide drill aimed at improving detection skills for space rocks and preparing Earth for a potential incoming threat.
On Tuesday, officials with IAWN admitted that the object was causing ‘unique challenges’ for predicting its trajectory and decided to add 3I/ATLAS to the Comet Astrometry Campaign.
The object has displayed several unusual features that defy the typical behavior of comets, including an ‘anti-tail,’ a jet of particles that points toward the Sun rather than away from it.
According to the release, scientists will be running a special training exercise from November 27, 2025, to January 27, 2026.
Telescopes and tracking systems around the world will focus on 3I/ATLAS to refine methods for pinpointing its exact location in the sky.
