Interstellar Comet 3I/ATLAS Exhibits Unprecedented Carbon Dioxide Levels
NASA's James Webb Space Telescope has identified interstellar comet 3I/ATLAS, discovered in July 2025, as possessing an unusually high carbon dioxide-to-water ratio, suggesting it formed in a distinct environment from our solar system.
NASA's James Webb Space Telescope (JWST) has observed interstellar comet 3I/ATLAS, revealing an exceptionally high carbon dioxide (CO₂) to water (H₂O) ratio in its coma. This discovery suggests the comet originated in an environment markedly different from our solar system.
Detected on July 1, 2025, by the ATLAS telescope in Chile, 3I/ATLAS is the third confirmed interstellar object to traverse our solar system. It is currently traveling at approximately 137,000 miles per hour and will reach its closest approach to the Sun on October 30, 2025, at a distance of about 1.4 astronomical units.
JWST's Near-Infrared Spectrograph (NIRSpec) instrument identified a CO₂-to-H₂O mixing ratio of 8:1 in the comet's coma, one of the highest ever recorded. This ratio is significantly higher than typical solar system comets, where water usually predominates.
The unusual chemical composition of 3I/ATLAS may indicate that it formed near the CO₂ ice line in its original protoplanetary disk or was exposed to higher levels of radiation, affecting its composition. Alternatively, the comet might possess an insulating crust that suppresses water sublimation while allowing CO₂ to escape.
Further analysis of 3I/ATLAS's trajectory suggests it originated from the Milky Way's thick disk, a region containing older, metal-poor stars. This implies the comet could be older than our 4.6-billion-year-old solar system.
While some have speculated about more exotic origins, current evidence supports 3I/ATLAS being a natural object with unique characteristics. Astronomers continue to monitor the comet as it approaches the Sun, aiming to gain further insights into its composition and origin.