New model explains how the Earth stole the Moon’s lighter elements

(credit: NASA)

The Earth and its Moon are very similar in composition, a fact that’s neatly explained by the idea that the two formed from the shared debris of a collision between the early Earth and a Mars-sized body. But there are some elements that show a distinctly uneven distribution between the two. If everything else is so similar between the two bodies, why are these exceptional?

It turns out that these elements are more volatile—they remain in a gaseous form at lower temperatures. And a new model of the Moon-forming collision suggests that, in the high temperatures of the collision debris, they remained gaseous until after the Moon moved out of the debris field.

The elements in question are metals that are relatively light—things like potassium, sodium, and zinc. Scientists noticed that the Earth had more of these elements than lunar samples; they suggested that it might have something to do with the fact that they remain gasses at lower temperatures than elements that were more evenly distributed. And there’s a simple way to explain this: the Moon formed while the temperatures were too high.

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New model explains how the Earth stole the Moon’s lighter elements