Linking Titan’s properties to its formation conditions

Abstract

Gas giant satellites are generally believed to form in circumplanetary disks (CPDs): a gas disk containing solid particles that accumulate to form moons over time. The discoveries by the Cassini­ Huygens mission have led to a revision of the birth environment of the Saturnian system. The aim of this thesis is to constrain the formation circumstances of Titan’s building blocks by considering the satellite’s observed characteristics, and identify the implications therefrom on Titan’s present state. We use the Protoplanetary Disk Modelling (ProDiMo) tool to model radiation thermo-­chemical CPDs, and evaluate them on their capacity to reproduce a Titan­like satellite. To form a moon with Titan’s ice-­to­-rock ratio, we find that the dust-­to-­gas ratio in the CPD must be in the order of solar nebula values, 푙표푔(푑/푔) = −2.05 ± 0.2. The ice availability upon accretion is otherwise incompatible with Titan’s moment of inertia. Our models predict a large NH3 inventory was available upon Titan’s formation, ∼10­-20wt.% of the total ice. Our findings are consistent with the hypothesis that the observed N2 in Titan is captured as NH3, and are compatible with the possible presence of a conductive layer at 45±15 km as revealed by the Huygens probe.