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24m ago

JWST Finds CO2-Dominated Coma Around Interstellar Visitor 3I/ATLAS

New spectra report an unusually high CO2-to-water ratio that bolsters the view that the object is a carbon‑rich comet.

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(Image Credit: David Jewitt/NASA/ESA/Space Telescope Science Institute (STScI), processed by Nrco0e.)
The mysterious interstellar comet 3I/ATLAS (Image Credit: ESA/Hubble)
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Overview

  • JWST NIRSpec detected a CO2-dominated gas coma at 3.32 au with a CO2/H2O mixing ratio of 8.0±1.0, one of the highest ever measured in a comet.
  • The JWST spectra show H2O, CO, OCS, water ice and dust, with outgassing enhanced toward the Sun.
  • Independent SPHEREx and IRTF observations also find strong CO2 emission and indicate a dust-dominated, carbon‑rich coma.
  • Most astronomers interpret the activity as natural cometary outgassing, while Avi Loeb continues to promote a technosignature hypothesis that remains unsubstantiated.
  • 3I/ATLAS follows a fast hyperbolic path with perihelion later this year inside Mars’s orbit and a closest Earth distance near 270 million kilometers when it will be obscured by the Sun.