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Carbon-rich icy moons and dwarf planets


IPGP - Îlot Cuvier


Séminaires thème Origines


Bruno Reynard

ENS Lyon

Dwarf planets and giant planets’ moons may record the original composition of the solar or planetary nebula. Previous models assumed essentially Earth-like silicate-metal cores surrounded by ice. Inner density models of the rocky cores of differentiated Ganymede and Titan, the largest icy moons in the solar system indicate the presence of a low-density component in addition to silicates and metal sulfide. Carbonaceous matter akin to coal formed from abundant organic matter in the outer solar system is a likely low-density component. We tested this hypothesis and found that rocky core densities in dwarf planets and icy moons are consistent with a mixture of chondritic silicate-sulfide rocks and a rock-free precursor composed of ices and carbonaceous matter in near-solar proportions. Thermal models taking into account the presence of carbonaceous matter are performed to evaluate its effects on the present-day structure of icy moons and dwarf planets.