Overview

• A Southwest Research Institute-led team used James Webb Space Telescope spectra near 3.3 microns to identify methane in the gas phase above the surface.
• The finding, detailed in an arXiv preprint with Astrophysical Journal Letters publication pending, marks only the second confirmed detection of gas on a trans-Neptunian object after Pluto.
• Modeling indicates one viable explanation is an extremely tenuous, equilibrium atmosphere with a temperature near 40 K and a surface pressure around 10 picobars.
• An alternative interpretation is transient plume-like outgassing releasing methane at rates of a few hundred kilograms per second, comparable in scale to Enceladus’ water plumes.
• Previous stellar occultations ruled out a substantial global atmosphere, and the team cites instrument noise and limited spectral resolution as reasons to pursue higher-resolution JWST follow-ups.