An inorganic silicate simulant to represent the interior of enceladus

Abstract

Enceladus, an icy moon of Saturn, consists of an ice shell, global subsurface ocean and a silicate interior. By sampling plume material, the Cassini spacecraft found evidence of ongoing water-rock reactions between the silicate interior and the subsurface ocean. These data showed that these reactions provide a source of bioessential elements to the ocean, making Enceladus one of the leading astrobiological targets in our Solar System. Understanding these water-rock reactions is critical in understanding the potential habitability of Enceladus. To study these reactions experimentally, a chemical simulant to represent the contemporary silicate interior of Enceladus has been designed. Based on the available interpretations of Cassini data about the density, chemical composition, and aqueous alteration of the interior, the chosen starting point for the simulant is a CI chondrite. However, Enceladus is still undergoing active aqueous alteration, thus its silicate mineral assemblage cannot have reached the fully altered assemblage seen in a CI chondrite. To account for this, adaptations have been made to a CI chondrite mineral assemblage, extrapolating back to an assemblage of less aqueously altered minerals whilst maintaining the same chemical composition in terms of major oxide phases. Thus, the chemical and mineralogical composition of this simulant represents a best estimate of the silicate components in the ongoing water rock interactions on Enceladus today.