Credit: NASA/JPL-Caltech/SETI Institute.
Beneath its icy outer shell, Europa, one of the moons of Jupiter, has a liquid ocean more than 100 kilometers deep, making it an important planetary body in the search for habitable or inhabited extraterrestrial environments. Like Earth, Europa’s ocean consists largely of liquid water (H2O) and other chemical species that may have a role in biological processes. Understanding how Europa’s ocean formed and evolved can help scientists determine how its potential for habitability has changed over time.
A study led by Mohit Melwani Daswani at NASA’s Jet Propulsion Laboratory examined the previously unconsidered hypothesis that early formation of a metallic core inside Europa, suggested by its high density, could have led to the development of its ocean. The team used a combination of chemical and thermodynamic models to determine what chemical reactions occurred as the formation of the iron core heated Europa’s interior to temperatures of at least 1000°C and whether those reactions could have released volatiles.
Their results suggest that core formation could have driven irreversible chemical reactions that released water, methane, and sulfur to form Europa’s ocean. If this was the case, the ocean should be rich in carbon dioxide (CO2) and calcium-sulfate-bearing (CaSO4) compounds, leading to precipitation of sulfate and carbonate minerals. They also predict a gradient in chlorine and sulfur abundance that is consistent with recent spectroscopic observations. In this model, Europa’s ocean was formed from indigenous materials, and no late delivery of volatile species from comets is necessary, as previously proposed. The presence of CO2 would be significant in facilitating biological processes, and thus represents an important component in understanding the habitability of Europa. READ MORE