Subaru Telescope team finds lower carbon dioxide-to-water ratio in 3I/ATLAS interior
Updated
Updated · Universe Today · May 5
Subaru Telescope team finds lower carbon dioxide-to-water ratio in 3I/ATLAS interior
4 articles · Updated · Universe Today · May 5
Using Jan. 7 observations after the interstellar comet's perihelion, researchers analysed its coma and said stronger outgassing exposed material from beneath radiation-altered outer layers.
The Astrophysical Journal study suggests 3I/ATLAS's coma chemistry is evolving and offers clues to the comet's internal structure, differing from ratios inferred earlier by space telescopes.
Detected by ATLAS in June 2025, 3I/ATLAS is the third known interstellar object; scientists say such studies could help compare planet-forming material from beyond and within the Solar System.
This interstellar visitor shed its outer layers. What does its newly exposed core tell us about its mysterious origins?
What does this comet's strange water chemistry reveal about the potential for life in other star systems?
Dramatic Shift in CO₂/H₂O Ratio Reveals Layered Chemistry of Interstellar Comet 3I/ATLAS
Overview
In 2026, observations of interstellar comet 3I/ATLAS revealed a dramatic change in its chemical makeup after passing close to the Sun. Initially, its coma was dominated by carbon dioxide, but intense solar radiation at perihelion vaporized deeper, water-rich layers within its heterogeneous nucleus. This caused a significant drop in the CO₂ to water ratio and the detection of methane, making its composition more similar to another interstellar comet, 2I/Borisov. The comet's layered structure formed in the cold outer regions of its home system, shaped by cosmic ray processing and temperature gradients. Despite these chemical differences, its dust properties resemble those of solar system comets, suggesting universal dust formation processes.