Diagram showing the interior of the Earth's Moon. The outermost layer, the crust, is about 70 km thick. This is thicker than the Earth's crust, which cooled down at a much slower rate. Beneath the crust is a thick silicate mantle, then a zone of partial melt with a radius of 480 km. This is probably where moonquakes occur. Current thinking, based on a re-examination of Apollo lunar seismometer data, is that the core, once thought solid, is now composed of a liquid outer component (330 km radius) and a solid inner one (240 km). [ + ] [ - ]

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