A Metamorphic Origin for Europa's Ocean

Abstract

Europa likely contains an iron‐rich metal core. For it to have formed, temperatures within Europa reached ≳1250 K. Going up to that temperature, accreted chondritic minerals — for example, carbonates and phyllosilicates — would partially devolatilize. Here, we compute the amounts and compositions of exsolved volatiles. We find that volatiles released from the interior would have carried solutes, redox‐sensitive species, and could have generated a carbonic ocean in excess of Europa's present‐day hydrosphere, and potentially an early CO2 atmosphere. No late delivery of cometary water was necessary. Contrasting with prior work, CO2 could be the most abundant solute in the ocean, followed by Ca2+, SO42−, and HCO3−. However, gypsum precipitation going from the seafloor to the ice shell decreases the dissolved S/Cl ratio, such that Cl>S at the shallowest depths, consistent with recently inferred endogenous chlorides at Europa's surface. Gypsum would form a 3–10 km thick sedimentary layer at the seafloor.