“Icy Moons and Trans-Neptunian objects as probes of a carbon-rich solar system” by Bruno Reynard (ENS Lyon)

Carbon-rich compositions are inferred from the densities and moments of inertia of Jovian and Saturnian icy moons, dwarf planets, and other trans-Neptunian objects (TNOs). Thermal models that account for the presence of carbonaceous matter show that originally hydrated silicates are now largely dehydrated in the refractory cores of large moons and dwarf planets, due to interactions with volatiles released by the metamorphism of carbonaceous matter. Progressive gas release from the slowly warming, carbonaceous matter-rich cores may sustain,
up to the present day, the replenishment of ice-ocean layers with organics and volatiles, as well as outgassing to the surface. This process accounts for the observation of nitrogen, light hydrocarbons, and complex organic molecules at the surface of moons and dwarf planets. The formation of large carbon-rich icy bodies in the outer solar system suggests that a carbon-rich environment prevailed during ice giant planet formation—a scenario that could also lead to the formation of carbon-rich planets at the outskirts of extrasolar systems.