The Mid-UV Spectrum of Irradiated NaCl at Europa-like Conditions
Recent observations from the Hubble Space Telescope show a mid-UV absorption feature localized to leading-hemisphere chaos regions on Europa. The same regions were previously found to have a visible absorption at 450 nm that was attributed to the presence of irradiated NaCl. The lack of any additional diagnostic absorptions for NaCl in the visible spectrum of these terrains made confirmation of this identification difficult. Here we use laboratory experiments to show that NaCl irradiated at Europa's surface temperatures develops an absorption at ∼220 nm, consistent with the new detection in Europa's mid-UV spectrum, strongly supporting the NaCl identification. Irradiated NaCl in leading-hemisphere chaos terrain would suggest that sodium and chlorine are important components of Europa's subsurface ocean.
Additional Information© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 July 30; revised 2021 December 3; accepted 2021 December 21; published 2022 February 2. This research was supported by a grant No. 668346 from the Simons Foundation.
Published - Brown_2022_Planet._Sci._J._3_28.pdf
Accepted Version - 2201.01335.pdf