A New UV Spectral Feature on Europa: Confirmation of NaCl in Leading-hemisphere Chaos Terrain

TL;DR

This study confirms the presence of irradiated sodium chloride on Europa's surface by detecting a new ultraviolet absorption feature that correlates with a known visible feature, indicating sodium chloride's role in Europa's geochemistry.

Contribution

The paper provides the first ultraviolet spectral confirmation of sodium chloride in Europa's leading-hemisphere chaos terrain, supporting its subsurface origin.

Findings

Detection of a new 230 nm absorption feature matching irradiated NaCl.

Spatial correlation of UV and visible features with chaos terrain.

Implications for Europa's subsurface composition and geochemistry.

Abstract

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.