JWST spots mysterious signature on Titan and Pluto, hinting at shared surface chemistry

Astronomers using the James Webb Space Telescope detected an identical, unexplained infrared absorption feature on both Saturn’s moon Titan and Pluto, suggesting a common, ground-based molecule formed by photochemistry in nitrogen/methane environments. The signal does not appear to be a biosignature and may belong to a family of hydrocarbons like allenes or a shifted fingerprint of a known molecule. The feature was seen by two JWST instruments (NIRSpec and MIRI), reducing the chance of an instrument artifact, and its ground-surface origin is supported by how the signal weakens from Titan’s center to its limb. Pluto’s near-vacuum atmosphere rules out atmospheric origin, pointing to the surface as the likely source. Researchers plan to map the signature across Titan’s surface and compare with Pluto's surface, with Dragonfly’s 2028 Titan mission expected to help identify candidates through in-situ analysis.