在远离太阳的外太阳系，在木星轨道之外，温度低到足以使冰从水以及甲烷和二氧化碳等气体中形成。
Far from the sun, in the outer solar system, beyond Jupiter's orbit, temperatures are low enough to permit ices to form out of water and out of gases like methane and carbon dioxide.
一开始你可能不会这样认为，因为太阳系里和彗星发生过碰撞的行星都比火星还远，在那样的轨道上水永远是以冰的形式存在。
On first blush, you might think not: the planet where the comet or comets came to grief is farther out than Mars, in an orbit where water would be permanently frozen.
这一理论严谨地解释了为什么太阳系中这一部分的大多数物体都是冰岩混合物，而土星的光环却近乎都是冰块。
The theory neatly accounts for why Saturn's rings are nearly pure ice, while most objects in that part of the solar system are more an ice-rock blend.
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