Abstract
Europa likely contains an iron-rich metal core. For it to have formed,
temperatures within Europa reached ≳1250 K. At that temperature,
accreted chondritic minerals - e.g., 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.