The explanation may be in Earth's mantle, the layer of rock underlying the tectonic plates and extending down over 1,800 miles to the outer edge of Earth's iron core.

解释可能是在地球的地幔中，这是在构造板块下面的岩石层，向下延伸超过1800英里到地球铁芯的外边缘。

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What the researchers found deep in the lunar interior: a solid iron ball 300 miles across, wrapped in molten iron another 56 miles thick, topped with a 93-mile layer of partially molten material.

研究人员发现在月球内部深处：有一个跨度约为300英里的固体铁球，包裹在另外56英里厚的铁水里，顶上部分地还有93英里层的熔融材料。

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The debris, which came from an asteroid that was once 125 miles long, showed little carbon and high levels of calcium and iron.

碎片来自125英里长的小游星，由微弱的碳和大量钙、铁组成。

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CMS's Consumers Energy unit has 626 miles of cast- and wrought-iron pipeline in its gas system, or about 2.4 percent of the utility's total distribution system.

WSJ: Report: Michigan a leader in outdated gas lines

Mr Putin said he had thanked God that no big fragments of the meteor - which was thought to be made of iron and travelling at some 30km (19 miles) per second - had fallen in populated areas.

BBC: Russia sends clean-up team to meteorite-hit Urals

Mr Ecclestone's companies have an iron grip on every frame that is shot within miles of a race--not just the actual contest, but the practice sessions and footage taken in the pits.

ECONOMIST: Mr Formula One