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JWST Finds Methane in Ancient Interstellar Comet 3I/ATLAS

6/2/2026

Summary

Story summary

James Webb Space Telescope detected methane gas in interstellar comet 3I/ATLAS, the first such detection.
MIRI recorded mid-infrared spectra on 15–16 Dec 2025 at 329 million km and on 27 Dec 2025 at 379 million km.
The comet’s rare methane-to-water ratio and carbon-dioxide abundance accompanied a drop in water-vapor output as it receded.
Scientists estimate the comet is about 10 billion years old, twice the Sun’s age, and that it formed beyond our Solar System.

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Story summary

James Webb Space Telescope detected methane gas in interstellar comet 3I/ATLAS, the first such detection.
MIRI recorded mid-infrared spectra on 15–16 Dec 2025 at 329 million km and on 27 Dec 2025 at 379 million km.
The comet’s rare methane-to-water ratio and carbon-dioxide abundance accompanied a drop in water-vapor output as it receded.
Scientists estimate the comet is about 10 billion years old, twice the Sun’s age, and that it formed beyond our Solar System.