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。

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By comparison, the terrestrial planets have meager atmospheres at best.

相比之下，类地行星最多只有稀薄的大气层。

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However, unlike Jupiter, the terrestrial planets today are nearly void of light gases and ices.

然而，如今的类地行星与木星不同，几乎没有轻气体和冰。

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Dr. THOMMES: We had have ordered a few percent of systems that where the giant planets at least resemble the architecture in our own system, as to whether we would then have terrestrial planets in the habitable zone, the chances of that actually aren't too bad, because the terrestrial planets, we think, they kind of sprout like mushrooms pretty much anywhere.

NPR: What Makes Our Solar System Special?

"It happened probably right at the end of the formation of the four terrestrial planets - Mercury, Venus, Earth and Mars, " said Craig Agnor, a co-author on the Francis Nimmo study.

BBC: Mars' two-faced riddle 'solved'

This is the process of differentiation and it is something evident in the fully formed terrestrial planets like Earth and Mercury.

BBC: A fleeting encounter with an 'inbetweener'