西南研究所的科学家结合了月球形成的动力学，热和化学模型，以解释月球岩石中相对缺乏挥发性元素。月球岩石在许多方面都与地球岩石非常相似，但是月亮岩石在钾，钠和锌等挥发性元素中更加耗尽，它们往往具有较低的沸点并容易蒸发。
“Explaining the Moon’s volatile depletion has been a long-standing mystery, and yet it is a key piece of evidence about how the Earth-Moon system formed,” said Dr. Robin Canup, associate vice president in SwRI’s Space Science and Engineering Division and lead author of the Nature Geoscience paper detailing the findings.
科学家认为，大约45亿年前的地球与另一个火星大小的身体之间的巨大影响产生的蒸气和熔融物质的土盘形成。以前，科学家认为，在月球形成之前，由于撞击而蒸发的挥发物可能已经逃脱了。
卡普说：“但是，实际上很少有挥发物丢失，因为逃脱地球重力所需的速度很高。”“相反，新的研究表明，随着月亮的生长，挥发性丰富的熔体优先沉积在地球上，而不是在生长的月亮上。”
Canup的团队（包括来自SWRI，Dordt College和Washington University的研究人员）进行了现有的计算机模拟，以对月球从磁盘积聚。这与磁盘材料的温度和化学成分如何随时间演化而结合使用。
The models show that the Moon acquires about the final half of its mass from melt condensed in the inner portions of the disk, close to the Earth and just inside the Moon’s initial orbit. Over time, the Moon’s orbit expands due to dynamical interactions with inner disk material. When the Moon is distant enough, it can no longer efficiently accumulate inner disk melt, which is instead scattered inward and assimilated by the Earth.
“We find that the inner disk melt remains hot and volatile-poor as it accretes onto the Moon. Eventually the disk cools and volatiles condense. But by the time this occurs the Moon’s accumulation from this inner disk region has essentially terminated,” said Canup. “So the final materials the Moon accumulates are lacking in波动元素，即使没有逃脱。”
作者建议，月亮最初从外磁盘积聚的材料可能是挥发性的，然后是最终的100至500公里的挥发性贫困材料。在这种情况下，根据月球内部混合的程度，月亮的挥发性含量可能会随着深度而增加。
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