Lunar magma ocean

The lunar magma ocean was a hypothesized global layer of molten rock that covered the early Moon. Its cooling and crystallization produced the Moon’s differentiated crust and mantle.

Fractional crystallization: The progressive separation of crystals from a cooling melt, changing the composition of the remaining liquid. Minerals crystallized in sequence and separated from the lunar melt as it cooled.
Planetary differentiation: The separation of a planetary body into layers with different compositions or densities. The magma ocean is a proposed early stage in the Moon’s separation into crust and mantle.
Giant-impact hypothesis: The leading model that the Moon formed from debris produced by a collision between early Earth and a planetary body. The energetic conditions of lunar formation could have melted much or all of the young Moon.
Apollo 11: The 1969 NASA mission that first landed astronauts on the Moon and returned lunar samples. Its samples included highland rocks used to investigate early lunar crust formation.
Lunar chronology: The reconstruction of the timing and sequence of events in the Moon’s geological history. Competing dates for lunar rocks affect estimates of when the magma ocean solidified.
Plagioclase: A group of feldspar minerals that forms a major component of many igneous rocks. Buoyant plagioclase crystals accumulated near the surface to form much of the lunar crust.
Silicate mineral: A mineral built primarily from silicon-oxygen groups combined with other elements. Silicate minerals made up most of the molten lunar material and its crystallized products.
Theia: The hypothesized protoplanet whose collision with early Earth produced debris that formed the Moon. The impactor’s collision is part of the formative event associated with the Moon’s early melt.
Lunar sample 60025: An Apollo 16 lunar highland rock classified as a ferroan anorthosite. Its ancient anorthositic composition is consistent with flotation from a lunar magma ocean.
Lunar isotopic composition: The distribution of stable and radioactive isotopes measured in lunar materials. Isotopic similarities and differences with Earth constrain lunar origin and early melting models.

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