Geology of the Moon

The study of the Moon’s materials, surface features, interior, and geological history. It explains how impacts, volcanism, and internal cooling shaped the lunar landscape.

Impact cratering: The formation of craters and related terrain when asteroids, comets, or other bodies strike a planetary surface. Impacts dominate lunar surface formation and excavate material from different depths.
Lunar regolith: The layer of loose, impact-ground rock and dust covering the Moon’s solid surface. This fragmented layer is the main material sampled by lunar missions.
Apollo program: The United States human spaceflight program that landed astronauts on the Moon between 1969 and 1972. Apollo returned rock samples that anchored lunar chronology and geochemical models.
Lunar chronology: The reconstruction of the timing and sequence of events in the Moon’s geological history. Crater counts and dated samples provide ages for surfaces that lack direct samples.
Giant-impact hypothesis: The leading model that the Moon formed from debris produced by a giant collision involving the early Earth. Lunar chemistry and isotope similarities constrain the collision’s conditions and resulting debris.
Lunar volcanism: The eruption and emplacement of molten rock on the Moon, chiefly during its early history. Ancient eruptions filled impact basins with the dark plains called maria.
Lunar mare: A broad, dark lunar plain formed mainly from basaltic lava erupted into an impact basin. Mare basalts preserve evidence of the Moon’s volcanic composition and chronology.
Luna program: A Soviet series of robotic lunar missions conducted from 1959 to 1976. Luna landers and sample-return missions added sites beyond the Apollo landing regions.
Lunar meteorite: A meteorite ejected from the Moon by an impact and later found on Earth. These samples extend lunar geology beyond the small set of mission landing sites.
Lunar farside: The hemisphere of the Moon that faces away from Earth, with thicker crust and few maria. Its contrasting crust and volcanism raise questions about lunar asymmetry.

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