The amount of water present in the moon may have been overestimated1 by scientists studying the mineral apatite（磷灰石）, says a team of researchers led by Jeremy Boyce of the UCLA Department of Earth, Planetary and Space Sciences. Boyce and his colleagues created a computer model to accurately2 predict how apatite would have crystallized from cooling bodies of lunar magma early in the moons history. Their simulations revealed that the unusually hydrogen-rich apatite crystals observed in many lunar rock samples may not have formed within a water-rich environment, as was originally expected.This discovery has overturned the long-held assumption that the hydrogen in apatite is a good indicator3 of overall lunar water content.The mineral apatite is the most widely used method for estimating the amount of water in lunar rocks, but it cannot be trusted, said Boyce, who is an adjunct assistant professor in the UCLA College of Letters and Science. Our new results show that there is not as much water in lunar magma as apatite would have us believe.The research was published online March 20 in the journal Science on and will be published in a future print edition.For decades, scientists believed the moon was almost entirely4 devoid5 of water. However, the discovery of hydrogen-rich apatite within lunar rocks in 2010 seemed to hint at a more watery6 past. Scientists originally assumed that information obtained from a small sample of apatite could predict the original water content of a large body of magma, or even the entire moon, but Boyces study indicates that apatite may, in fact, be deceptive7.Boyce believes the high water content within lunar apatite results from a quirk8 in the crystallization process rather than a water-rich lunar environment. When water is present as molten rock cools, apatite can form by incorporating hydrogen atoms into its crystal structure. However, hydrogen will be included in the newly crystallizing mineral only if apatites preferred building blocks, fluorine and chlorine, have been mostly exhausted9.Early-forming apatite is so fluorine-rich that it vacuums all the fluorine out of the magma, followed by chlorine（氯）, Boyce said. Apatite that forms later doesnt see any fluorine or chlorine and becomes hydrogen-rich because it has no choice.Therefore, when fluorine and chlorine become depleted10, a cooling body of magma will shift from forming hydrogen-poor apatite to forming hydrogen-rich apatite, with the latter not accurately reflecting the original water content in the magma.
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1 overestimated 对（数目）估计过高，对…作过高的评价 参考例句： They overestimated his ability when they promoted him. 他们提拔他的时候高估了他的能力。 The Ministry of Finance consistently overestimated its budget deficits. 财政部一贯高估预算赤字。
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