Mysterious Interstellar Comet 3I/ATLAS Challenges Comet Science with Unusual Activity and Composition
October 11, 2025
Interstellar object 3I/ATLAS exhibits a unique composition, with a high ratio of carbon dioxide to water and unusual chemical signatures, indicating its interstellar origin.
This water outpouring at such a distance hints at alternative processes beyond solar sublimation, implying the comet may have substantial water reserves and other unknown activity mechanisms.
Astronomers believe 3I/ATLAS originated from the Milky Way's center, likely ejected from its original star system billions of years ago, making it a relic from an earlier cosmic era.
Recent analysis using NASA's Swift telescope reveals 3I/ATLAS is releasing large quantities of water vapor, indicated by ultraviolet emissions of hydroxyl gas, which is unusual at its current distance.
Currently, 3I/ATLAS is behind the Sun but has been observed by spacecraft near Mars, with visibility expected to improve in late November.
Despite being about three astronomical units from the Sun, 3I/ATLAS is ejecting water at roughly 88 pounds per second, a rate that suggests activity driven by mechanisms other than solar heating.
These findings highlight that interstellar objects like 3I/ATLAS are expanding our understanding of planetary system diversity and challenging previous assumptions about comet formation and composition.
Summary based on 1 source
Get a daily email with more Science stories
Source

Futurism • Oct 11, 2025
Interstellar Object Is Spraying Something Weird, Scientists Find