Comets consist of "dirty ice", rather than solid rock, and so contain little iridium.

彗星是由“脏冰”所组成，而不是像小型那样由固体岩石组成，所以只含有少量的铱。

youdao

Since plants had not yet evolved 700 million years ago, the dirty ice could have been the only dark spots on Earth's surface to absorb the sun's rays.

7亿年前地球上还没有植物，浑浊的冰（泥土和冰的混合物）可能是地球表面唯一能够吸收阳光的黑色物质。

youdao

The ground is covered with moraine. Ice under it is gray and dirty.

地表覆盖着冰碛石。底部的冰呈灰色并且肮脏。

youdao

We have a pretty good idea that they're made of dirty ice, but beyond that, we don't really know the details of what they're made of.

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When the ice sheets were thick and advancing, more pebbles, stones, and dirty sediment would have been carried into the core by the moving ice.

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