Knowra Earth's Moon Earth's Moon Earth's Moon is Earth's only permanent natural satellite. It formed early in Solar System history and is the largest natural satellite relative to its planet.
Lunar orbit : The Moon's path around Earth, shaped mainly by their mutual gravity and the Sun's influence. Its elliptical, slowly evolving path determines the Moon's distance, motion, and eclipses.
Giant-impact hypothesis : The leading explanation that the Moon formed from debris produced by a collision between early Earth and a planetary body. It explains the Moon's formation while accounting for key similarities between lunar and terrestrial material.
Selenography : The mapping and description of the Moon's surface features. This field names and charts the terrain that defines lunar geography.
Apollo program : The United States human spaceflight program that landed astronauts on the Moon between 1969 and 1972. Apollo missions returned samples that transformed knowledge of lunar geology and history.
Natural satellite : A celestial body that orbits a planet, dwarf planet, or other larger body without being an artificial object. The Moon belongs to the broader population of natural satellites.
Lunar phases : The changing visible shapes of the Moon as sunlight illuminates different portions of its Earth-facing hemisphere. The Moon's changing appearance follows its position relative to Earth and the Sun.
Theia : A hypothesized planetary body whose collision with early Earth may have produced the debris that formed the Moon. The proposed impactor is central to the Moon's leading formation model.
Lunar regolith : The layer of loose dust, soil, and broken rock covering much of the Moon's solid surface. Impacts continually grind lunar rocks into the material encountered at the surface.
Lunar sample : Rock, soil, or other material collected from the Moon for scientific study. Returned samples allow precise laboratory measurements unavailable from remote observations alone.
Phobos : The larger and innermost natural satellite of Mars, a small irregular body on a rapidly decaying orbit. Its tiny size and irregular form contrast with the large, differentiated Moon.
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