Knowra Moon Moon Earth’s natural satellite is a differentiated rocky body whose heavily cratered surface records impacts, volcanism, and a long history of geological change.
Lunar phases : The changing illuminated shapes of the Moon seen from Earth as the Moon orbits the planet. The Moon’s phase depends on the changing geometry among the Sun, Earth, and Moon.
Lunar regolith : The loose layer of fragmented rock, dust, and impact debris covering the Moon’s solid surface. This impact-ground material blankets nearly every exposed lunar terrain.
Giant-impact hypothesis : The hypothesis that the Moon formed largely from debris ejected when a planetary body struck the early Earth. It is the leading explanation for the Moon’s origin and unusual Earth-like composition.
Apollo 11 : The 1969 Apollo mission that made the first crewed landing on the Moon. Its landing and returned samples mark the first direct human exploration of the lunar surface.
Earth : The third planet from the Sun and the only known world with life on its surface. The Moon’s composition, size, and geological activity are often compared with its parent planet.
Tides : Periodic changes in sea level caused chiefly by the gravitational attraction of the Moon and Sun. The Moon’s gravity produces the largest astronomical contribution to Earth’s ocean tides.
Lunar maria : Large, dark plains on the Moon formed mainly by ancient basaltic lava flows. Their smooth, dark surfaces contrast with the older, brighter lunar highlands.
Theia : A hypothesized protoplanet whose collision with early Earth may have produced the Moon. The proposed impactor gives the giant-impact hypothesis its central role for lunar formation.
Lunar sample : Rock, soil, or other material collected on the Moon and returned or analyzed for scientific study. Samples from lunar missions provide direct evidence of surface composition and geological history.
Mars : The fourth planet from the Sun, a rocky world with a thin atmosphere and ancient geological record. Comparing Mars and the Moon separates shared impact history from differences in atmosphere and geology.
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