The Cassini-Huygens mission that explored the Saturn system during the period 2004–2017 revolutionized our understanding of Titan, the only known moon with a dense atmosphere and the only body, besides Earth, with stable surface liquids. Its predominantly nitrogen atmosphere also contains a few percent of methane that is photolyzed on short geological timescales to form ethane and more complex organic molecules. The presence of a significant amount of methane and ⁴⁰Ar, the decay product of ⁴⁰K, argues for exchange processes from the interior to the surface. Here we review the information that constrains Titan's interior structure. Gravity and orbital data suggest that Titan is an ocean world, which implies differentiation into a hydrosphere and a rocky core. The mass and gravity data complemented by equations of state constrain the ocean density and composition as well as the hydrosphere thickness. We present end-member models, review the dynamics of each layer, and discuss the global evolution consistent with the Cassini-Huygens data.

2004 年至 2017 年期间探索土星系统的卡西尼-惠更斯号任务彻底改变了我们对土卫六的理解，泰坦是唯一已知的具有稠密大气层的卫星，也是除地球之外唯一具有稳定表面液体的天体。其主要是氮的大气还包含百分之几的甲烷，这些甲烷在很短的地质时间尺度上被光解形成乙烷和更复杂的有机分子。甲烷的显著量和存在⁴⁰的Ar，的衰变产物⁴⁰K主张从内部到表面的交换过程。在这里，我们回顾了限制泰坦内部结构的信息。重力和轨道数据表明泰坦是一个海洋世界，这意味着分化为水圈和岩石核心。由状态方程补充的质量和重力数据限制了海洋密度和组成以及水圈厚度。我们展示了最终成员模型，回顾了每一层的动态，并讨论了与 Cassini-Huygens 数据一致的全球演化。