Fate of sulfate in Europa's ocean: hydrothermal reactions, experimental insights, and implications for future missions
Abstract
Recent observations of Europa's surface suggest that a large quantity of exogenic sulfate originated from Io would have been supplied into its subsurface ocean. Despite the importance of sulfate to Europa's oceanic chemistry, little is known about its fate within the ocean. Here we report our experimental results on sulfate reduction in hydrothermal environments under the conditions comparable to Europa's seafloor. Using a newly-developed experimental system capable of performing on-line sampling of hydrothermal fluids during the experiments at 130 MPa and 300 deg.C., we first obtain the reaction rates of sulfate reduction under Europa's hydrothermal conditions. By introducing the experimental results into thermochemical equilibrium calculations of water-rock reactions, we also show that, if Europa's seafloor rock is basaltic, exogenic sulfate would be effectively consumed by hydrothermal reactions, leading to occurrence of a Na, Mg, H2S, and Cl-rich ocean. On the other hand, if Europa's rock is still chondritic, sulfate would accumulate within the ocean, resulting in occurrence of a Na and SO4-rich ocean. We propose that identification of salts on Europa's surface and in plumes through future missions would be critical to constrain Europa's rock composition and possible occurrence of hydrothermal activity.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E3054S