Some facts about the Moon. | |||||||||||||||||||||||||||||||||
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The Moon is the Earth only natural satellite. It is a barren, heavily
cratered world, lacking water or an atmosphere. Tidel forces have ensured
that the same side of the Moon now always faces the Earth. As the Moon
travels round the Earth in the course of a month, it undergoes the familiar
cycle of phases. The Moon shines only by reflected sunlight; the proportion
of the sunlit side visible from Earth depends on the relative alignment of
the Sun, Earth and Moon, which changes continuously over the Moon's orbital
period. The terrain on the nearside falls into two basic types: the heavily cratered, light-coloured highlands, and the darker, more sparsely cratered maria (seas). The maria have roughly circular outlines, a relic of their formation in the early history of the Moon by the impact of large meteorites. |
The way the Moon formed is uncertain, but it has existed as a separate
body for around 4,500 million years. Early in its life it became hot and
molten. As it cooled, the crust formed but it was heavily cratered by impact
of large numbers of meteorites, the largest of which created the mare
basins. These subsequently filled with dark basaltic lavas. Significant
volcanic activity then ceased, at least 2,000 million years ago. The mean distance from Earth to the Moon is 384,400 km. The Moon's radius is 1,738 km; mean density is 3.34 g/cm3. | ||||||||||||||||||||||||||||||||
Apollo Missions.
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Luna Missions.
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