Sodium chloride on the surface of Europa
Abstract
The potential habitability of Europa's subsurface ocean depends on its chemical composition, which may be reflected in that of Europa's geologically young surface. Investigations using Galileo Near-Infrared Mapping Spectrometer data led to the prevailing view that Europa's endogenous units are rich in sulfate salts. However, recent ground-based infrared observations have suggested that, while regions experiencing sulfur radiolysis may contain sulfate salts, Europa's more pristine endogenous material may reflect a chloride-dominated composition. Chlorides have no identifying spectral features at infrared wavelengths, but develop distinct visible-wavelength absorptions under irradiation, like that experienced on the surface of Europa. Using spectra obtained with the Hubble Space Telescope, we present the detection of a 450-nm absorption indicative of irradiated sodium chloride on the surface. The feature correlates with geologically disrupted chaos terrain, suggesting an interior source. The presence of endogenous sodium chloride on the surface of Europa has important implications for our understanding of its subsurface chemistry.
Additional Information
© 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S.Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 17 January 2019. Accepted 3 May 2019. Published 12 June 2019. Based on observations made with the NASA/ESA HST, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. These observations are associated with program number 14650. We thank G. R. Rossman for useful conversations. This work was supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program (grant 80NSSC17K0478). Support for this work was provided by NASA through grant number HST-GO-14650.001-A from the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555. This research was supported by grant 1313461 from the NSF. K.P.H. acknowledges support from the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA and funded, in part, through the internal Research and Technology Development program. Author contributions: S.K.T. performed the analysis and wrote the manuscript. M.E.B. conceived and designed the observations. K.P.H. helped conceive the observations and provided laboratory spectra. All authors discussed the results and interpretations and provided helpful comments on the manuscript. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. The data used in this work are also available at the NASA Mikulski Archive for Space Telescopes under program number 14650. Additional data related to this paper may be requested from the authors. The authors declare that they have no competing interests.Attached Files
Published - eaaw7123.full.pdf
Supplemental Material - aaw7123_SM.pdf
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Additional details
- PMCID
- PMC6561749
- Eprint ID
- 96448
- Resolver ID
- CaltechAUTHORS:20190614-125339605
- NAS 5-26555
- NASA
- 80NSSC17K0478
- NASA Earth and Space Science Fellowship
- HST-GO-14650.001-A
- NASA
- AST-1313461
- NSF
- NASA/JPL/Caltech
- JPL Research and Technology Development Fund
- Created
-
2019-06-14Created from EPrint's datestamp field
- Updated
-
2022-02-25Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, Division of Geological and Planetary Sciences