Abstract
Abstract Recent visible-wavelength observations of Europa’s surface obtained with the Hubble Space Telescope (HST) 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 HST 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.
Highlights
Salt hydrates sourced from Europa’s putative subsurface ocean have long been proposed as components of its geologically young surface (e.g., McCord et al 1998), which could allow remote-sensing studies to constrain the ocean’s composition and chemical history
Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) spectroscopy, we detect a previously unseen absorption feature near 230 nm, which we attribute to V3 centers of irradiated NaCl
The feature appears strongest within leading-hemisphere chaos terrain, Tara Regio, and corresponds geographically to the proposed F-center absorption of NaCl detected in recent visiblewavelength HST data
Summary
P. Denman , Philippa Molyneux , Amanda Hendrix , Kurt D. Retherford , Lorenz Roth , and Juan Alday. Received 2021 July 30; revised 2021 November 4; accepted 2021 November 16; published 2022 February 2
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