Composition of Frozen Brines in the Aqueous Na-Mg-SO4 and Na-Mg-Cl Systems
Abstract
Analysis of the Galileo mission data and subsequent laboratory research have shown that Europa's surface is rich in non-ice materials (primarily sulfates and chlorides), which may have endogenic and/or exogenic origins. The Europa Lander mission concept aims at understanding the habitability of Europa's internal ocean, which the composition of non-ice materials of endogenic origin will provide chemical context for (e.g. dissolved ionic species and concentrations, pH). Evaporitic environments on Earth suggest a myriad of possible salt compositions, including multiple-cation-bearing salts and variable hydration states, some of which (e.g. bloedite) have been suggested to explain in part the Galileo data. However, not only is the temperature significantly lower on Europa than in terrestrial evaporitic environments, but water is also significantly more abundant and the only process that may affect availability of water is surface processing. Thus, to better understand the composition of icy minerals that may form from freezing of brines on Europa's surface, we conducted an experimental investigation of the aqueous Na-Mg-SO4 and Na-Mg-Cl systems via cryogenic differential scanning calorimetry and Raman spectroscopy. Only single cation salts have been observed, namely mirabilite and meridianiite/epsomite for the SO4-bearing solutions, and hydrohalite and a magnesium chloride hydrate for the Cl-bearing solutions. A cryogenic X-ray diffraction study in underway to further investigate these chemical systems and confirm the results. These results suggest a reduced set of potential icy mineral phases of endogenic origin on Europa's surface, which may be used to constrain spectral mixing models. Further, unambiguous detection of multiple-cation-bearing salts on the surface might indicate their formation via exogenic processes.
Acknowledgements: This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Support from the NASA Astrobiology Institute ("Icy Worlds" node) and government sponsorship acknowledged.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P21E3387V
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 4599 General or miscellaneous;
- OCEANOGRAPHY: PHYSICALDE: 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 6299 General or miscellaneous;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS