Lunar interior

Lunar interior

Fig. 5.22 . A schematic cross section of the Moon shows its internal structure. The lunar crust is thinner on the near side that faces the Earth, and thicker on the far side. Fractures in the thin crust have allowed magma to reach the surface on the near side, where the lava-filled maria are concentrated. The Moon has an iron-rich core with a radius of about 20 percent of the Moon's average radius of 1,738 kilometers. A partially molten layer is believed to encircle the Moon’s core, out to depths of about 1,000 kilometers. The Moon's center of mass (CM) is offset by 2 kilometers from its center of figure, CF, so an equipotential surface, which experiences an equal gravitation force at all points, lies closer to the lunar surface on the hemisphere facing Earth. Therefore magmas originating at equipotential depths will have greater difficulty reaching the surface on the far side.

Copyright 2010, Professor Kenneth R. Lang, Tufts University