Early on, dense iron sank out of the magma oceans to form the metallic core, liberating enough gravitational energy to melt the entire planet.是什么意思_Early on, dense iron sank out of the magma oceans to form the metallic core, liberating enough gravitational energy to melt the entire planet.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句