" 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."

“最大的是三，不是四，”她从罗恩身后指着他那篇天文学论文中的行文字说道，“有火山的应该是。”

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

第二大是四（卡利斯托），直径约4800公里。

The ESA took the opportunity to do a test run of Juice's instruments, which it will use to look for molecular signatures of habitability on the moons Europa, Ganymede and Callisto.

欧洲航天局借此机会对 Juice 的仪器进行了测试，这些仪器将用于寻找二、三和四上适宜居住的分子特征。

In 1610, for example, Galileo used the first telescope to discover Jupiter's moons Io, Callisto, Europa, and Ganymede — now known as the Galilean Moons.

例如，1610 年，伽利略用第台望远镜发现了的、四、二和三，这些现在被称为伽利略。

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利略——四、二和三，这三颗都被认为拥有地下海洋。

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，，二，三，四。

They're called Ganymede, Callisto, and Europa.

这几个分别叫三、四和二。

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，可能和四同岁。

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

在四个大行中，四的公转轨道离最远，约达200万千米。

It has a magnetic field, too, but it probably doesn't have a metallic core.

四也有磁场，但是它的核应该不是金属态核。