The Moon’s Interior

(b) Based on seismic experiments left on the Moon by Apollo astronauts and the studies done by Lunar Prospector,
we know that the Moon has a crust, a mantle, and a core. The lunar crust has an average thickness of about 60 km
on its Earth-facing side but about 100 km on the far side. The crust and solid upper mantle extend to about 800 km,
where the nonrigid inner mantle begins. The Moon’s core has a radius of between 300 and 425 km. Although the
main features of the Moon’s interior are analogous to those of Earth, the proportions and details are quite different.
The Clementine spacecraft revealed that the south pole has a significant basin. The crust was apparently stripped
away by an impact. Top inset: A radar image of the Moon’s north polar region. The areas computer-colored in white
and light gray are regions where the Sun never shines and that may contain water. Bottom inset: A radar image of
the Moon’s south polar region, also showing regions of permanent or near-permanent darkness.