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Theorists are divided concerning theorigin of the Moon. Some hypothesize that the Moon was formed in the same wayas were the planets in the inner solar system (Mercury, Venus, Mars, andEarth)—from planet-forming materials in the presolar nebula. But, unlike thecores of the inner planets, the Moon’s core contains little or no iron, whilethe typical planet-forming materials were quite rich in iron. Other theoristspropose that the Moon was ripped out of the Earth’s rocky mantle by the Earth’scollision with another large celestial body after much of the Earth’s iron fellto its core. One problem with the collision hypothesis is the question of how asatellite formed in this way could have settled into the nearly circular orbitthat the Moon has today. Fortunately, the collision hypothesis is testable. Ifit is true, the mantlerocks of the Moon and the Earth should be the samegeochemically. 地幔那个是这一篇吗 |
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