  Recent visible-wavelength observations of Europa's surface obtained with the
Hubble Space Telescope revealed the presence of an absorption feature near 450
nm that appears spatially correlated with leading-hemisphere chaos terrain.
This feature was interpreted to reflect the presence of irradiated sodium
chloride ultimately sourced from the interior. Here, we use ultraviolet spectra
also collected with the Hubble Space Telescope to detect an additional
previously unseen absorption near 230 nm, which spatially correlates with the
450 nm feature and with the same leading-hemisphere chaos terrain. We find that
the new ultraviolet feature is also well-matched by irradiated sodium chloride
at Europa-like conditions. Such confirmation of sodium chloride within
geologically young regions has important implications for Europa's subsurface
composition.
