Deciphering the Origin of the Regular Satellites of Gaseous Giants - Iapetus: the Rosetta Ice-Moon

Abstract

Here we show that Iapetus can serve to discriminate between satellite formation models. Its accretion history can be understood in terms of a two-component gaseous subnebula, with a relatively dense inner region, and an extended tail out to the location of the irregular satellites, as in the SEMM model of Mosqueira and Estrada (2003a,b). Following giant planet formation, planetesimals in the feeding zone of Jupiter and Saturn become dynamically excited, and undergo a collisional cascade. Ablation and capture of planetesimal fragments crossing the gaseous circumplanetary disks delivers enough collisional rubble to account for the mass budgets of the regular satellites of Jupiter and Saturn. This process can result in rock/ice fractionation provided the make up of the population of disk crossers is non-homogeneous, thus offering a natural explanation for the marked compositional differences between outer solar nebula objects and those that accreted in the subnebulae of the giant planets. Consequently, our model leads to an enhancement of the ice content of Iapetus, and to a lesser degree those of Ganymede, Titan and Callisto, and accounts for the (non-stochastic) compositions of these large, low-porosity outer regular satellites of Jupiter and Saturn. (abridged)

33 pages, 7 figures, 2 tables, Accepted for publication to Icarus

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• Formation of moon systems around giant planets: Capture and ablation of planetesimals as foundation for a pebble accretion scenario
• Pebble accretion at the origin of water in Europa
• Saturn's formation and early evolution at the origin of Jupiter's massive moons
• The formation of the Galilean moons and Titan in the Grand Tack scenario
• Stability of Ice/Rock Mixtures with Application to a Partially Differentiated Titan
• Planetesimals and Satellitesimals: Formation of the Satellite Systems
• Large mass inflow rates in Saturn's rings due to ballistic transport and mass loading