Page 55 - Curriculum Visions Dynamic Book

The Moon does not have a magnetic field like the Earth, which suggests that the core is not molten or moving. Nevertheless, Moon rocks do show some traces of magnetism, and so a magnetic field did exist on the Moon in the past.
Many of these changes can be related to the fact that the Moon is so much smaller than the Earth. As a result, any heat it once had in its core has long ago flowed to the surface by condUction and been radiated to space.
Without this source of heat the churning movements of a molten core are not possible. Nonetheless, some very small “moon” quakes (seismic activities) still occur.
The point is, however, that the Moon was not always an inactive world. Certainly, billions of years ago the Moon quite suddenly became extremely hot, so much so that a crust formed over a core, and huge volcanoes sent lava flows over the surface. The mascons occur where the lava is thickest.
center of gravity The point at which all of the mass of an object can be balanced.
condUction The transfer of heat between two objects when they touch.
core The central region of a body.
crUst The solid outer surface of a rocky body.
density A measure of the amount of matter in a space.
gravity The force of attraction between bodies.
isotope Atoms that have the same number of protons in their nucleus, but that have different masses; for example, carbon-12 and carbon-14.
magnetic field The region of influence of a magnetic body.
magnetism An invisible force that has the property of attracting iron and similar metals.
mantle The region of a planet between the core and the crust.
mare (pl. maria) A flat, dark plain created by lava flows. They were once thought to be seas.
mascon A region of higher surface density on the Moon.
molten Liquid, suggesting that it has changed from a solid.
orbit The path followed by one object as it tracks around another.
radiate The transfer of energy in the form of waves (such as light and heat) or particles (such as from radioactive decay of a material).
radioactive The property of some materials that emit radiation or energetic particles from the nucleus of their atoms.
Crust. Thickest on the side facing away from Earth.
 A possible internal structure for the Moon.
Asthenosphere. There may also
be a metallic core.
Craters
60-100 km
re-scan
about 740 km
1,740 km
Mare
Mantle (lithosphere)
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