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1·Hence, the Jovian planets are often called giants.

因此，木星行星通常被称为巨行星。

2·The most obvious difference between the terrestrial and the Jovian planets is their size.

类地行星和类木行星之间最明显的区别是它们的大小。

3·The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen, helium, methane, and ammonia.

木星的行星有非常厚的大气层，且由不同数量的氢、氦、甲烷和氨等元素组成。

4·Also, because of their relative locations, the four Jovian planets are known as the outer planets, while the terrestrial planets are known as the inner planets.

同样，由于它们的相对位置，四颗类木行星被称为外行星，而类地行星被称为内行星。

5·The densities of the terrestrial planets average about 5 times the density of water, whereas the Jovian planets have densities that average only 1.5 times the density of water.

类地行星的密度的平均值大约是水的密度的五倍，而类木行星的密度平均值只有水的密度的1.5倍。

6·Also, because the molecular motion of a gas depends on temperature, at the low temperatures of the Jovian planets even the lightest gases are unlikely to acquire the speed needed to escape.

此外，由于气体的分子运动依赖于温度，在木星行星的低温下，即使是最轻的气体也不可能获得逃逸所需的速度。