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Project Progress

S. Desch with his group continued their work on thermal structure and evolution models of Kuiper belt objects (KBOs) and small icy satellites. The models have been updated to account for crystalline/amorphous ice transition and for Rayleigh-Taylor instabilities within the body. These models predict the likelihood of subsurface water and cryovolcanism on these bodies. A paper is being prepared for publication (Rubin & Desch 2012, in prep).
Chemical disequilibria inside the Saturnian icy moon Enceladus have been evaluated by M. Zolotov in the context of habitability and reactivity of organic species in putative aqueous environments. The comet-like abundances of major plume gases and apparent redox disequilibria in aquatic systems are consistent with a minimal influence of aqueous processes on endogenic chemical reactions and may indicate abiotic interior.
M. Zolotov used chemical equilibrium models to evaluate fluid composition and pH during aqueous alteration of CI carbonaceous chondritic materials, which may represent rocks in icy bodies. The results show that fluid chemistry is mainly affected by solubility of secondary minerals, concentration and speciation of Cl in initial water(ice)-rock mixtures, and degree of sulfide to sulfate conversion in oxidized conditions. If sulfates do not form, solutions are represented by NaCl-rich compositions with lesser amounts of HCO₃-, CO₃^2-, K⁺ and organic solutes. The models are consistent with the detection of NaCl-Na₂CO₃ bearing grains emitted from Enceladus.

Chemical processes responsible for formation and evolution of oceans on icy moons have been discussed in a review paper published in Space Science Reviews. Another review paper on chemistry of Enceladus (Zolotov et al.) is prepared for submission.
M. Zolotov participated in interpretation of Cassini Neutral and Ion Mass Spectrometer and Cosmic Dust Detector data obtained for plume emissions of Enceladus.
Graduate student Chris Glein is putting the finishing touches on a thermodynamic model to compute solubilities of gases and solids in liquid hydrocarbon lakes on the surface of Saturn’s moon Titan.