Composition and stability of salts on the surface of Europa and their oceanic origin

Research output: Contribution to journalArticle

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Abstract

We present theoretical models of the composition, the relative abundances, and the stability of hydrated salts on the surface and in the icy shell of Jupiter's satellite Europa and discuss whether those salts have an oceanic origin. The evaluations were done with thermodynamic calculations of (1) salt dehydration equilibria at the conditions of the surface of Europa and its icy shell, (2) chemical equilibria involving solids and water vapor in the Na-K-Mg-Ca-S-Cl-H2O system at surface temperatures and variable partial pressures of water vapor, and (3) changes in aquatic chemistry and sequences of salt precipitation from freezing oceanic water, using cosmochemical, mass balance, and physical-chemical constraints on the elemental and ionic composition of the ocean. Mass balance calculations of total or partial extraction of elements into an ocean from a carbonaceous chondrite type mantle show that magnesium and sulfate rather than chloride and sodium could be the most abundant solutes in the ocean. Freezing oceanic water of this composition leads to brines that differ in composition from the original water and to deposition of ice and highly hydrated sulfates of Mg, Na, and Ca as well as alkali chlorides. After freezing is complete, highly hydrated salts remain stable in ice-bearing surface materials and throughout the icy shell. For hypothetical surface salt lag deposits, formed through sublimation/sputtering of ice and dehydration of salts, we predict hydration stratification with depth, approaching the highest hydration states in ice-bearing materials in the lowest parts of the deposits. We discuss the effects of fast disequilibrium freezing and variable dehydration rates of salts on the predicted mineral assemblages at the surface. All of our models, which are independent of observations, predict the predominance of Mg and Na sulfates in surface salts, in agreement with spectroscopic models for the nonicy surface material in the near infrared spectral region.

Original languageEnglish (US)
Pages (from-to)32815-32827
Number of pages13
JournalJournal of Geophysical Research E: Planets
Volume106
Issue numberE12
StatePublished - Dec 25 2001
Externally publishedYes

Fingerprint

Europa
Salts
salts
salt
Ice
Chemical analysis
Freezing
freezing
Bearings (structural)
Dehydration
ice
dehydration
sulfates
Steam
oceans
mass balance
Hydration
shell
sulfate
Sulfates

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Composition and stability of salts on the surface of Europa and their oceanic origin. / Zolotov, Mikhail; Shock, Everett.

In: Journal of Geophysical Research E: Planets, Vol. 106, No. E12, 25.12.2001, p. 32815-32827.

Research output: Contribution to journalArticle

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