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The Moon is Earth's only natural satellite, orbiting at an average distance of 384 399 km (238,854 mi; about 30 times Earth's diameter). It faces Earth always with the same side. This is a result of Earth's gravitational pull having synchronized the Moon's rotation period with its orbital period (lunar month) of 29.5 Earth days.
The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to "lunar science") is quite different from that of Earth. The Moon lacks a true atmosphere , and the absence of free oxygen and water eliminates erosion due to weather .
Selenography is the study of the surface and physical features of the Moon (also known as geography of the Moon, or selenodesy). [1] Like geography and areography , selenography is a subdiscipline within the field of planetary science .
The Moon's heavily cratered far-side. The origin of the Moon is usually explained by a Mars-sized body striking the Earth, creating a debris ring that eventually collected into a single natural satellite, the Moon, but there are a number of variations on this giant-impact hypothesis, as well as alternative explanations, and research continues into how the Moon came to be formed.
Lunar corona A solar corona up Beinn Mhòr (South Uist). In meteorology, a corona (plural coronae) is an optical phenomenon produced by the diffraction of sunlight or moonlight (or, occasionally, bright starlight or planetlight) [1] by individual small water droplets and sometimes tiny ice crystals of a cloud or on a foggy glass surface.
An alternative definition is that the penumbra is the region where some or all of the light source is obscured (i.e., the umbra is a subset of the penumbra). For example, NASA 's Navigation and Ancillary Information Facility defines that a body in the umbra is also within the penumbra.
Mining the moon for water, helium-3, and rare earth elements could become a multibillion-dollar industry in the near future, but astronomers warn it risks coming at the expense of scientific ...
The "harvest moon" (also known as the "barley moon" or "full corn moon") is the full moon nearest to the autumnal equinox (22 or 23 September), occurring anytime within two weeks before or after that date. [18] The "hunter's moon" is the full moon following it. The names are recorded from the early 18th century. [19]