Endogenous CO 2 ice mixture on the surface of Europa and no detection of plume activity.

Jupiter's moon Europa has a subsurface ocean beneath an icy crust. Conditions within the ocean are unknown, and it is unclear whether it is connected to the surface. We observed Europa with the James Webb Space Telescope (JWST) to search for active release of material by probing its surface and atmosphere. A search for plumes yielded no detection of water, carbon monoxide, methanol, ethane, or methane fluorescence emissions. Four spectral features of carbon dioxide (CO 2 ) ice were detected; their spectral shapes and distribution across Europa's surface indicate that the CO 2 is mixed with other compounds and concentrated in Tara Regio. The 13 CO 2 absorption is consistent with an isotopic ratio of 12 C/ 13 C = 83 ± 19. We interpret these observations as indicating that carbon is sourced from within Europa.