The James Webb Space Telescope (JWST) has observed the interstellar comet 3I/ATLAS, revealing a surprisingly high concentration of carbon dioxide (CO₂) in its coma, a finding that sets it apart from other comets studied in our solar system. The observations, made on August 6, suggest an unusual chemical composition that could offer new insights into its origins beyond our sun.
Comet 3I/ATLAS, the third interstellar object ever confirmed, was first spotted in July by the ATLAS survey in Chile. Initial data from the JWST’s Near-Infrared Spectrograph (NIRSpec) showed that the comet’s coma—the cloud of gas and dust surrounding its nucleus—is dominated by carbon dioxide. The ratio of CO₂ to water is one of the highest ever recorded for a comet, an astonishing 16 times greater than expected for an object at its distance from the sun.
Researchers propose two main theories for this high CO₂ content. The comet’s nucleus may be intrinsically rich in carbon dioxide, possibly because it formed near the “carbon dioxide ice line” in its parent star’s protoplanetary disk. Alternatively, the ices within the comet may have been exposed to much higher levels of radiation than those found in our solar system, altering its chemical makeup.
While the JWST’s findings are groundbreaking, they align with data from other missions, including the recently launched SPHEREx and the Hubble Space Telescope, which have also noted the comet’s unusual composition and behavior. The comet is traveling on a hyperbolic trajectory and will continue its journey out of the solar system after its closest approach to the sun in October. Astronomers will continue to study this ancient visitor, which is potentially billions of years older than our own solar system, to uncover more about its mysterious past.