This drawing shows what the interior of the Moon might be like.
Click on image for full size
The Crust & Interior of the Moon
The picture shows the moon's crust, about 60=150 km thick, followed by the lithosphere, shown in blue. The moon's lithosphere is the major portion of the interior, about 1000 km thick. The moon's core may be comprised of two zones, a "soft" partially molten zone and a solid iron zone, as shown in the picture. Moonquakes, as measured by seismometers left behind by the Apollo astronauts, seem to take place between the outer core and the lithosphere.
The Moon's crust is a composed of a dusty outer
rock layer called a regolith. The term regolith refers to a rocky layer resembling concrete, which has been broken and blasted apart, then fused back together somehow. Like the Earth's crust, the Moon's crust seems to contain some magnetism. Both the crust and
regolith of the Moon are unevenly distributed over the entire
Moon. The crust ranges from 38 miles (60 km) on the
near side to 63 miles (100 km) on the far side. The
regolith varies from 10 to16 feet (3 to 5 meters) in
the maria to 33 to 66 feet (10 to 20 meters) in the
highlands. Scientists think that such asymmetry of
the lunar crust most likely accounts for the Moon's
off-set center of mass. Crustal asymmetry may also
explain differences in lunar terrain, such as the
dominance of smooth rock (maria) on the near side of
The Lunar Prospector Mission expects to explore more about the crust of the Moon. The Doppler Gravity Experiment onboard the spacecraft will explore expected asymmetries in the crustal structure and permit a more accurate
calculation of the so-called homogeneity constant, a
number which enables scientists to determine the
density of the lunar core. This is important
information for designing fuel-efficient future
lunar missions and landing operations.
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