High pressure and low temperature equations of state for aqueous magnesium sulfate: applications to the search for life in extraterrestrial oceans, with particular reference to Europa

Abstract

A prevalence of cold, high pressure (P > 100 MPa) environments in the Solar System, and beyond, is discussed in the context of contemporary efforts to understand the origin and abundance of life in the Universe. Constraints on the depths of fluid circulation in extraterrestrial seafloors are explored through a model for the development of microfractures in olivine through cooling. For the example of Europa, we estimate a factor of four in per-unit-area hydrogen flux from serpentinization as compared with calculations for Earth's seafloor. Uptake of seafloor salt by an incipient thermal plume is suggested as a stay on buoyancy and a driver for stratification in the Europa's ocean. An apparatus for optical measurements in deep-ocean analogue materials is described. Laser-induced phonon spectroscopy is applied to the determination of the velocity of sound in water and in aqueous solutions of MgSO4. The equation of state is deduced for concentrations from 0 to 2.0137 m for temperatures from -20 to 100°C and pressures as high as 700 MPa. Debye Huckel theory is employed for calculating partial molal volume at infinite dilution. The volumetric contribution of MgSO4 is less than expected above 200 MPa and at the extremes of temperature, indicating a change in ion-water interaction due to increased confinement under these conditions.