尽管金星和水星没有卫星，火星却有两个卫星，更别提各有超过60个卫星的土星和木星。
While Venus and Mercury have no moons, Mars has two, while Saturn and Jupiter have more than 60 each.
土卫六一直以来都是这项探测任务的主要聚焦点，因其体积比水星还要大，是唯一一颗拥有浓密大气层的卫星。
Titan was a major focus of the mission all along, since it's bigger than the planet Mercury and the only moon massive enough to have a significant atmosphere.
水星与地球的卫星月球看上去有些相似，只是它更大，密度更高，表面引力几乎是月球的两倍。
Larger, denser, and with almost twice the surface gravity of Earth's moon, Mercury still looks moon-like at first glance.
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