THE OCEANS OF EUROPA AND GANYMEDE. AQUEOUS SOLUTION UNDER PRESSURE AS POTENTIAL HABITATS

1. THE OCEANS OF EUROPA AND GANYMEDE. AQUEOUS SOLUTION UNDER PRESSURE AS POTENTIAL HABITATS O. Prieto-Ballesteros (1), V. Muñoz-Iglesias (1) and L. Jiménez Bonales (1, 2) (1) Centro de Astrobiología. INTA-CSIC, Madrid, Spain (2) Complutense University, Madrid, Spain

2. Motivation • There are some indirect evidences of the presence of liquid reservoirs in the interior of Europa and Ganymede. There are no direct data about the characteristics of aqueous cryomagmas yet. Cryomagmatic processes have interest for Astrobiology because involve relative warm water rich liquids • Simulation experiments can provide some knowledge about the chemical reactions and geological processes that can be expected to occur at subsurface conditions • The information that we already have about the endogenic materials at the surface, the geochemical models of the satellite, and the geophysical models about the internal structure, are used for setting up the experiments • Experiments: • Crystallization of gas clathrates from salty solutions • Solubility of gases under pressure in salty solutions • Processes of fractional crystallization of cryomagmas Evolution of aqueous liquids Environmental constraints for habitability

3. Constraints EUROPA • Pressure. We consider a total pressure range from 1 to 1800 bar, taking into account a water ice crust of 20km (≈240 bar) and a total water-rich layer of 100-150 km (cryomagmas ascend into the crust) • Temperature , dependent on the solution composition • Composition. We assume the aqueous composition is mainly sulfate rich, with CO2 (sulfuric acid and other salts are also considered)

4. Equipment • Two different high pressure chambers located at Centro de Astrobiología (CAB-INTA-CSIC), Madrid, are available for making these experiments: • HPPSC (High Pressure Planetary Simulation Chamber), which working pressure range is 1-3000bar (extendable up to 10000 bars), the sample volume is 10ml. It has four ports for making different in situ analysis, including sapphire windows for optical measurements • MPPSC (Moderate-high pressure Planetary Simulation Chamber), which maximum working pressure is 300bar, the volume is variable up to 50ml due to a mobile piston. It also has a window for spectroscopic measurements Both chambers are made of stainless steel and have automatic control system for temperature and pressure. Raman and ultraviolet spectroscopy have been the main techniques used during the experiments.

5. Pressuretransducer V1 V3 P Pressuretransducer P V2 Sapphire window Thermal fluid CO2 Laser CCD Hydraulic compressor Optic system Optic Fibers High Pressure Chamber Thermocouple Monochromator HPPSC

6. MPPSC

7. Clathrate formation from MgSO4 solutions There were not any experiment on CO2-clathrates formed from MgSO4-H2O in the literature Salts are inhibitors of clathrate formation. Sulfates affects less than chlorides Theoretical models shows a decrease of temperature of 3-4 degrees in the dissociation line

8. Procedure for clathrate formation Clathrates are formed from a solution saturated in CO2 and different concentration of MgSO4 (5, 10, 17% weight) Formation cycle: ABCD Analysis of the kinetic of clathrate formation by Raman Calibration: evolution of the brine using the SO42- peaks

9. Raman monitoring of clathrate formation

10. Evolution of the solution CO2 bands (1280 and 1380 cm-1): Fermi bands are displaced, hot bands disappear SO42- band change during the formation of clathrates. It increases in the first moment, and finally decreases if saturation of the salt produce its precipitation

11. Application to europa Formation of clathrates in aqueous reservoir may produce the fractional differentiation of the cryomagmatic liquids A: H2O-CO2-MgSO4cryomagmatic chamber B: CO2clathrates crystallize C: Brine concentrates and separates, salts can precipitate D: Dissociation by P/T change. Clean H2O-CO2cryomagmas can erupt

12. Solubility of CO2 in salty solutions There are solubility data of CO2 in some brines at different pressures (chlorides, Na-sulfate) but not MgSO4 and just to relative high pressures Solubility CO2 in a brine 22% Na2SO4

13. Effect of pressure on the solubility of CO2 in MgSO4 Dependence of the CO2 solubility in a 3% MgSO4 solution with pressure. This analysis have been done for different concentrations of sulfate

14. Application to europa Buoyancy of briny cryomagmas and style of the eruption Cryomagmas charged in gas can suffer exolution if they depressurize to form a foam that has low density 0.01 Pressure (MPa) 0.06

15. Aplication to europa Following the terrestrial models, if volume% of gas is up to 75% of cryomagma, fragmentation would occur and the cryomagma could erupt violently to the surface Depth where the pressure for fragmentation can be reached in the crust of Europa

16. Conclusions Cryomagmatic liquids have astrobiology interest The evolution of cryomagmas from the interior of Europa may occur by several processes (final products, including biosignatures could be the exposed materials at the surface) Simulation in laboratory may help to understand how these processes occur • Clathration may be a style of differentiation in icy satellites • Exolution of gases in sulfate-rich aqueous cryomagmas may derive in briny cryomagma buoyancy and explosive cryovolcanism