The formation of clathrites under planetary conditions of ocean worlds: The case of Ceres and implications for future missions

Carbonates have been identified on the surfaces of several ocean worlds, although their formation processes remain poorly understood and are currently the subject of debate. Theoretical models have suggested the presence of clathrate hydrates in the subsurface of these ocean worlds and their dissociation could not only trigger the formation of certain kinds of surface geological features, but also contribute to the precipitation of authigenic carbonates emplaced on them. These authigenic carbonates, when derived from clathrate hydrate dissociation, are known as clathrites, which, to date, have only been reported on Earth along continental margins where clathrate hydrate deposits are present. In this work, we investigated whether the hypothetical precipitation of planetary clathrites could occur through the reaction between carbon molecules released after clathrate hydrate dissociation and brines or cryomagmas. We reproduced experimentally the formation process of clathrites from CO2-clathrate hydrates, monitoring in situ formation with Raman spectroscopy, and additionally characterised the mineral products ex situ by X-ray diffraction and IR spectroscopy. Here we show that carbon can be transferred from the dissociated clathrate hydrate molecules to the forming carbonates under the temperature-pressure conditions of the subsurface of ocean worlds. These high-pressure experimental results demonstrate that clathrites can form under crustal conditions of ocean worlds and that a genesis linked to clathrate hydrates should be considered, if the occurrence of these phases in the subsurface cannot be ruled out.