Physical properties of cryovolcanic brines: Applications to the evolution of Ganymede

Carbonaceous chondrites contain abundant veins of water soluble salts, including carbonates and hydrated sulfates of Mg, Ca, Na, Ni, and Fe. These constitute over 1/4 of the mass of the meteorite Orgueil. Magnesium sulfate is the most abundant salt, constituting nearly half the mass of all salt components combined (anhydrous), and 73 pct. of the highly water soluble salts. The assumption that icy satellites and asteroids contain rock compositionally similar to carbonaceous chondrites suggests that salts may be important in the cryoigneous evolution of icy satellites and asteroids. Ordinary chondrites, an alternative rock component of icy satellites, lack abundant salts, although their anhydrous silicate assemblages are unstable with respect to water and would react to produce salts upon initial melting of ice. Some basic physiochemical properties are reviewed of likely cryovolcanic brines and how the existence of soluble salts in Ganymede might affect its structure and evolution is considered. Observations indicate late stage (post heavy bombardment and post tectonic) volcanism on Ganymede. The highly fluid character of Ganymedian volcanism is consistent with extrusions of either water or salt water brines.