T207 The Big Picture from Small Worlds: Dwarf Planets, Trans-Neptunian Objects, Asteroids, Comets, and More

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

RHEOLOGICAL INVESTIGATION OF CRYOVOLCANIC BRINES: VISCOSITY OF CHLORIDE AND SULFATE BRINES

Paper number: T207-18
Program: Technical Sessions
Time: 5:12 PM – 5:22 PM

Authors

Abstract

Rheological properties of potential cryovolcanic products are fundamental in determining how flows are emplaced and what morphologies result. Evolving cryogenic compositions span a similar viscosity range as silicate lavas allowing similar morphologies to occur (e.g. domes or flows). Few experimental studies have been conducted to provide rheological data relevant to cryovolcanism. A broad compositional range of liquids need to be fully characterized to investigate the effect of crystallization. We conduct measurements of briny liquids to model viscosity as a function of temperature and composition.

Binary aqueous salt systems [NaCl, KCl, NH4Cl, MgSO4, K2SO4, (NH4)2SO4] were chosen for their simplicity, well characterized nature, and relevance to cryovolcanism on Europa. Three concentrations on the water-rich side of the eutectic were synthesized for each composition. Isothermal liquid viscosity measurements were made at intervals between 30°C and -20°C. Cooling experiments (2, 1, and 0.5 K/min) were also run to provide information about viscosity evolution during undercooling and the kinetics of crystallization onset.

MgSO4 shows the most variation in viscosity for both temperature and concentration. At 0°C the viscosity of pure water is ~1.5 mPas, while the viscosity of 5 and 15 wt% solutions are 2.0 and 5.5 mPas. Viscosity increases to 5 and 14 mPas respectively at -20°C. For the other compositions, the same concentrations have less effect on viscosity, which range from 1.3 – 2.3 mPas at 0°C and from 2.5 – 4.5 mPas at -20°C. The viscosity of Europa’s ocean at the base of the ice crust is likely to be of the order of 2 mPas at an approximate liquidus temperature of 0°C.

Continued work will include measurements of methanol, ammonia, and carbonate systems. Viscosity measurements will also be conducted for higher concentrations on the solute-rich side of the eutectic. This will provide better constraints on physical and fluid dynamic evolution of flows on icy worlds.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-354378

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