The Moon: Internal Structure
Top Ten Scientific Discoveries Made During Apollo Exploration of the Moon
- The Moon is not a primordial object; it is an evolved terrestrial
planet with internal zoning similar to that of Earth.
- The Moon is ancient and still preserves an early history
(the first billion years) that must be common to all terrestrial
- The youngest Moon rocks are virtually as old as the oldest
Earth rocks. The earliest processes and events that probably
affected both planetary bodies can now only be found on the Moon.
- The Moon and Earth are genetically related and formed from
different proportions of a common reservoir of materials.
- The Moon is lifeless; it contains no living organisms, fossils,
or native organic compounds.
- All Moon rocks originated through high-temperature processes
with little or no involvement with water. They are roughly divisible
into three types: basalts, anorthosites, and breccias.
- Early in its history, the Moon was melted to great depths
to form a "magma ocean." The lunar highlands contain
the remnants of early, low density rocks that floated to the surface
of the magma ocean.
- The lunar magma ocean was followed by a series of huge asteroid
impacts that created basins which were later filled by lava flows.
- The Moon is slightly asymmetrical in bulk form, possibly
as a consequence of its evolution under Earth's gravitational
influence. Its crust is thicker on the far side, while most volcanic
basins -- and unusual mass concentrations -- occur on the near
- The surface of the Moon is covered by a rubble pile of
rock fragments and dust, called the lunar regolith, that contains
a unique radiation history of the Sun which is of importance to
understanding climate changes on Earth.
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