Will 3I/ATLAS Break Up?
On October 29, 2025, the interstellar object 3I/ATLAS will reach perihelion at a distance of 203 million kilometers from the Sun.
So far, no small objects were clearly associated with 3I/ATLAS in astronomical data sets. The latest images released by ESA’s ExoMars TGO (accessible here) show faint features around 3I/ATLAS that are likely noise artifacts. There are unrelated images of contemporary comets, background stars and the moons of Mars — Phobos and Deimos. But so far, there are no verified objects that branched off 3I/ATLAS.
Any object related to 3I/ATLAS in images from Mars orbiters or terrestrial telescopes, as well as any new activity of unidentified objects in the Earth’s atmosphere — which is being monitored by the Galileo Project observatories, would be of great interest in deciphering the nature of 3I/ATLAS.
If 3I/ATLAS is a comet of natural origin, it could disintegrate into fragments as it comes closer to the Sun. We should keep our eyes on this fuzzy ball of light and check whether it breaks up into independent smaller dots of light.
Comets disintegrate primarily as a result of heating by the sun, but sometimes also by gravitational tides and rotational stress from outgassing. The catastrophic breakup of a comet into multiple fragments is difficult to forecast without knowing its detailed composition and material strength.
Studies of comets like 67P/Churyumov-Gerasimenko show that they may have formed from smaller pieces that gently coalesced, leading to a poorly cemented structure with many internal fractures which makes these objects susceptible to break ups.
When a comet gets close to the sun, solar radiation heats its icy nucleus. Volatile ices, like carbon dioxide, carbon monoxide or water, sublimate directly into gas, carrying away dust and small rocks. Smaller objects have a larger surface area per unit mass, making them more vulnerable to excess heating and further mass loss. This process can cause the comet to break apart if the mix of ice and dust cannot withstand the resulting thermal stress.
The jets of sublimated gas are not distributed evenly across the comet’s surface and act like thrusters, spinning up the nucleus. Fast rotation could also break up the comet as inferred for comet 332P/Ikeya-Murakami, whose rapid spin likely led to its fragmentation (see discussion here). Breakup from gravitational tides was demonstrated in 1994, when the fragments of comet Shoemaker-Levy 9, torn apart by Jupiter’s gravity, crashed into the planet (see discussion here).
A fleet of smaller objects could also appear as a result of a technological mothership which releases min-probes to study multiple targets simultaneously. Smaller mass probes require less power for maneuvers aimed at exploration or self-replication in many locations at once.
Shortly after 3I/ATLAS will pass closest to the Sun, it will be observable by ESA’s Jupiter Icy Moons Explorer (Juice) during the month of November. During November and December, terrestrial observatories will also be able to monitor 3I/ATLAS and check whether it disintegrates like a natural comet or releases mini-probes as a technological mothership. The latter act might define 3I/ATLAS as an interstellar gardener, resembling a dandelion flower which spreads its genetic information through numerous seeds.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
