Composition, structure and evolution of Uranian and Neptunian satellites

Abstract

Large uncertainties in the current estimated densities or all of these satellites prevent detailed modeling or predictions. Nevertheless, current evidence suggests that at least Titania and Oberon might have "anomalously" high densities (2-3 g cm^)-3)), possibly requiring almost ice-free hydrated silicates or formation in a CO-rich environment, implying presence or co-clathrate and a small ice/rock ratio. Triton and the four largest satellites or Uranus are massive enough to have undergone significant accretional heating and early differentiation; NH_3-H_2O volcanism; partial outgassing or CO, N_2, CH_4; formation or dark surficial deposits or carbon-rich material obtained by UV irradiation or outgassed material; and, at least in the cases or Ariel and Triton, a possibility or weak ongoing icy volcanic activity. Triton may be the largest captured body in the solar system, with an unusual history and composition, including the possibility or substantial liquid or solid nitrogen obtained from either primordial NH_3 photolysis or clathrate decomposition.