What is the primary bulk chemical composition of the Moon, specifically focusing on the major elements and their approximate weight percentages in the lunar crust, mantle, and core? Furthermore, how does this composition compare and contrast with that of the Earth, and what implications does this have for the prevailing theories about the Moon’s formation, such as the giant-impact hypothesis? Please include details about the presence and distribution of key minerals like plagioclase feldspar, pyroxene, and olivine.
Answer
The Moon’s primary composition consists of silicate rocks and metallic iron.
Specific Details:
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Mantle: The lunar mantle is primarily composed of olivine, pyroxene, and smaller amounts of other minerals. It makes up the majority of the Moon’s volume.
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Crust: The lunar crust is primarily composed of plagioclase feldspar. The highland regions of the Moon’s crust are particularly rich in anorthosite, a rock composed almost entirely of plagioclase. Other minerals found in the crust include pyroxene and olivine. The crust is thicker on the far side of the Moon than on the near side.
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Core: The Moon has a small core, estimated to be approximately 2% of its total mass. This core is primarily composed of iron, with potentially some nickel and sulfur. It is believed to have a solid inner core and a fluid outer core.
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Regolith: The lunar surface is covered by a layer of loose, unconsolidated material called regolith. This material is composed of dust, rock fragments, and impact debris created by billions of years of meteorite impacts. It also contains small amounts of solar wind particles that have been implanted into the surface.
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Trace Elements: The Moon also contains trace amounts of other elements, including titanium, aluminum, magnesium, calcium, and potassium. These elements are found in varying concentrations in different regions of the Moon.
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Volcanic Glasses: Lunar volcanic glasses, which are small beads of solidified lava, are also found on the Moon’s surface. These glasses can provide information about the Moon’s volcanic history and the composition of its mantle.
- Absence of Water: The Moon is generally considered to be very dry, with only trace amounts of water ice found in permanently shadowed craters near the poles. The lunar rocks and regolith are also very dry, lacking the hydrated minerals that are common on Earth.