Abstract
Europa, an icy moon of Jupiter, is a prime candidate in the search for extraterrestrial life due to strong evidence of a subsurface liquid water ocean. Previous observations from the Hubble Space Telescope and re-analysis of Galileo data have suggested the presence of transient water vapor plumes erupting from Europa's south polar region, providing a potential direct pathway to sample the ocean's composition without needing to drill through kilometers of ice. However, definitive, high signal-to-noise detection and characterization of these plumes have remained challenging. This study utilized the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) to conduct high-resolution spectroscopic observations of Europa's limb. We report the unambiguous detection of gaseous water vapor absorption features in the mid-infrared spectrum, spatially localized to regions consistent with prior plume detections. Spectral analysis allowed for the characterization of the plume's column density and estimated temperature, confirming the active release of material from Europa's interior. These direct spectroscopic observations provide crucial insights into the dynamics of Europa's ocean-ice shell interface and significantly advance our understanding of this ocean world's astrobiological potential.
