Earth's moon, Saturn's Titan, Jupiter's Callisto, or Jupiter's Ganymede?

地球的卫星，土星的土卫六，木星的木卫四，还是木星的Ganymede?

They're called Ganymede, Callisto, and Europa.

这几个分别叫木卫三、木卫四和木卫二。

The next biggest moon is Callisto, at 4800 km in diameter.

第二大卫星是木卫四（卡斯托），直径约4800公里。

That means the surface is very old, maybe as old as Callisto itself.

这意味着它的表面非常古老，可能和木卫四同岁。

Callisto orbits Jupiter farthest out of the four biggies, almost two million km away.

四个大行星中，木卫四的公转轨道离木星最远，约达200万千米。

The four largest moons, Io, Europa, Ganymede, and Callisto, are large enough to be seen from Earth with a telescope.

从地球上就可以用望远镜看到最大的四颗卫星，木卫一，木卫二，木卫三，木卫四。

Juice will investigate three of the so-called Galilean moons-Callisto, Europa and Ganymede, all of which are thought to have subsurface oceans.

“果汁”探测器将调查三颗所谓的伽略卫星——木卫四、木卫二和木卫三，这三颗卫星都被认为拥有地下海洋。

" Jupiter's biggest moon is Ganymede, not Callisto, " she said, pointing over Ron's shoulder at a line in his Astronomy essay, " and it's lo that's got the volcanoes."

“木星最大的卫星是木卫三，不是木卫四，”她从罗恩身后指着他那天学论中的一行字说道，“有火山的应该是木卫一。”