An experimental estimate of Europa's "ocean" composition independent of Galileo orbital remote sensing

We have conducted a series of experiments designed to simulate, in the laboratory, the development of any subsurface aqueous phase on Europa. In our theoretical-experimental approach we select a single natural sample (a CM meteorite) that based on cosmochemical considerations, we consider to approximately represent the bulk material that accreted to form Europa. We then subject the sample to a hot water leaching procedure designed to simulate low- to moderate-temperature aqueous alteration. The resulting leach solution was then subjected to a series of sequential fractional crystallization steps producing a series of ices and residual brines. Then all this brines and ices are multiply analyzed for Na, Ca, Mg, Sr, Ba, Fe, Mn, K, Cl, and SO,. Results were found to be remarkably consistent between brines and ices in the same stages of crystallization and also between stages. We found that any putative aqueous phase below Europa's ice crust is probably a brine with cations: Na similar to Mg > Ca, K > Fe and anions: SO4 > > Cl. Our results are in harmony with inferences drawn from one of the two main current interpretations of the orbital spectral data but cannot definitively rule out inferences drawn from the alternative interpretation. This is so because the mineralogy of the top 200 mum may not reflect the chemical composition of bodies of brine below the solid surface owing to extensive alteration caused by magnetospheric bombardment.