Earth’s gravity may have kept the early moon’s volcanic heart beating

We typically think of the moon as a static, floating object that has remained the same for basically its entire lifetime, with an occasional asteroid impact serving as an exception. That understanding is grounded in physics-the moon should have cooled rapidly after forming when a huge protoplanet hit the early Earth around 4.5 billion years ago. But some lunar material returned from the Chang’e-5 mission was notably formed only around 2 billion years ago, yet appeared to be volcanic in origin.
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