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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L23203, doi:10.1029/2007GL031234, 2007

An oceanic composition on early and today's Enceladus

Mikhail Y. Zolotov

School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA


Abstract

The oceanic composition on Saturn's moon Enceladus is evaluated through calculations of thermochemical equilibria at hydrothermal and freezing settings. Conditions of rock alteration are constrained from assumptions and models for the moon's interior composition and thermal evolution, and from the composition of Enceladus' plume. Results show that an early ocean was an alkaline Na+-Cl−-HCO3 − solution. Underlying altered rocks consisted of Mg-phyllosilicates, magnetite, Fe and Ni sulfides, and carbonates. Subsequent freezing of oceanic water caused the deposition of a NaCl hydrate, Na, K and Ca carbonates, and the formation of a salt-free ice shell. If an aqueous phase exists on today's Enceladus, it could consist of eutectic Na-Cl-HCO3 − brine that at least locally decouples the ice shell and facilitates tidal heating. A lack of firm detection of Na and Cl at Enceladus is consistent with the accumulation of salts at the ice-rock boundary and implies the plume formation via sublimation in the ice shell.

Received 4 July 2007; accepted 12 November 2007; published 13 December 2007.

Keywords: Enceladus; ocean; composition.

Index Terms: 6280 Planetary Sciences: Solar System Objects: Saturnian satellites; 6040 Planetary Sciences: Comets and Small Bodies: Origin and evolution; 1060 Geochemistry: Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008); 1034 Geochemistry: Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424); 1009 Geochemistry: Geochemical modeling (3610, 8410).

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Citation: Zolotov, M. Y. (2007), An oceanic composition on early and today's Enceladus, Geophys. Res. Lett., 34, L23203, doi:10.1029/2007GL031234.