“James Webb uncovers a cosmic comet with mind-blowing chemistry in our solar system!”
Throughout history, comets have been interpreted as omens, messengers, or simple icy relics of the cosmos. But the newcomer doesn’t fit into any of those molds. Discovered in 2025 and now being observed by the James Webb Space Telescope, this interstellar body shows a composition unlike any comet in the solar system. Its ephemeral journey and chemical characteristics are intriguing.
### A First Look from the James Webb
The James Webb Space Telescope, the most powerful observatory ever launched into space, managed to capture a unique image of the comet. The infrared spectrum revealed an unexpected finding: the comet’s coma is dominated by carbon dioxide, accompanied by water, carbon monoxide, ice, and dust.
In this case, the proportion of carbon dioxide and water reaches levels never seen in comets observed at similar distances from the Sun. This suggests that the core of the comet itself is saturated with this gas, making it chemically distinct from any comet formed in our stellar neighborhood.
### Differences from Other Interstellar Travelers
To date, only three interstellar visitors have been confirmed: ‘Oumuamua, Borisov, and ATLAS. Of them, only Borisov and ATLAS showed visible comas. Borisov’s was dominated by water, while ATLAS’s shows a clear dominance of carbon dioxide.
In solar system comets, water is usually the main driver of activity, sublimating as they approach the Sun. 3I/ATLAS breaks that rule. Astronomers believe that the comet formed in a more hostile environment, exposed to much higher levels of radiation than bodies in our system experience.
### A Relic Older than the Sun
Calculations suggest that 3I/ATLAS could be 7,000 million years old, much older than the 4,500 million years of the solar system. This means that its existence predates the formation of our own planet and that it carries within it a chemical memory of previous stellar epochs.
Observations also confirmed that the comet releases between 6 and 60 kilograms of dust per second and small amounts of water, even before crossing regions where this type of sublimation usually occurs. These characteristics make it a cosmic time capsule.
### The Future of 3I/ATLAS
The comet travels at a speed of 61 kilometers per second and measures between 0.32 and 5.6 kilometers in diameter. Its hyperbolic trajectory will take it to a closest approach of 1.8 astronomical units from Earth – about 270 million kilometers – so it poses no danger.
After reaching its perihelion on October 29, 2025, 3I/ATLAS will definitively move away from the solar system. By the end of 2026, its brightness will have faded beyond the orbit of Jupiter, leaving behind only the data and questions we manage to obtain during its brief visit.
The James Webb, along with other observatories, now has the mission of taking advantage of this fleeting encounter to unravel the history of a comet that came from the depths of the Milky Way.
