The interstellar comet 3I/ATLAS, which has become only the third known object from beyond the Solar System, exhibits unique properties that distinguish it from other comets studied by humanity. As of April 2026, this object has already crossed Jupiter’s orbit and is rapidly leaving the Solar System, not returning.
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Chemical Composition and Behavior of the Comet
In October 2025, 3I/ATLAS approached the Sun at a minimum distance of 203 million kilometers, and by December, it passed at a distance of 270 million kilometers from Earth. It was during this time that the Webb Space Telescope observed it, allowing astronomers to gather an unprecedented amount of data for analysis.
Research has shown that as it moves away from the Sun, the comet actively ejects water vapor, carbon dioxide, and methane into space. While such gas emissions are typical for comets, 3I/ATLAS stands out with an unusually high content of carbon dioxide and methane compared to water. Experts believe that this comet formed long before the Solar System appeared and has been traveling through interstellar space for over a billion years.
“Interestingly, compared to comets in the Solar System, 3I/ATLAS contains more carbon dioxide than water, and more methane than water. This comet is believed to be much older than the Solar System and has been traveling through interstellar space for a very long time, at least a billion years.”
Differences from Other Interstellar Objects
Previous interstellar objects, such as 1I/‘Oumuamua and 2I/Borisov, did not exhibit similar methane emissions. In particular, 2I/Borisov is recognized as an interstellar comet, while the nature of 1I/‘Oumuamua remains a subject of debate within the scientific community. None of these objects displayed the same level of activity as 3I/ATLAS.
Experts note that 3I/ATLAS is not only faster and larger than its predecessors but also has a different composition. This may indicate different conditions of its formation or the influence of a unique environment in which it has existed during billions of years of travel from another star system.
- Comet 3I/ATLAS ejects significant volumes of water, carbon dioxide, and methane into space.
- Its composition is radically different from that of comets in the Solar System.
- Astronomers plan to continue monitoring it until the end of spring 2026 to obtain new scientific data.
Researchers also emphasize that, according to their calculations, 3I/ATLAS ejects about 2 tons of water into space every second. Continued study of this unique interstellar object may shed light on how comets form and evolve in different parts of the galaxy.