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This page refers to Earth's Moon. For other moons in the solar system, please see natural satellite. See also: the Luna program of unmanned space missions.
Moon craters (magnify) Over time, comets and meteorites continually bombard the Moon. Water-rich meteorites and comets, largely water ice, may leave significant traces of water on the lunar surface. Energy from sunlight splits much of this water into its constituent elements hydrogen and oxygen, both of which usually fly off into space immediately. Some water molecules, however, may have literally hopped along the surface and gotten trapped inside craters at the lunar poles. Due to the very slight "tilt" of the Moon's axis, only 1.5°, some of these deep craters never receive any light from the Sun - they are permanently shadowed. It is in such craters that scientists expect to find frozen water if it is there at all. If found, water ice could be mined and then split into hydrogen and oxygen by solar panel-equipped electric power stations or a nuclear generator. Such components could make space operations as well as human colonization on the Moon possible. Although the equatorial Moon rock collected by Apollo astronauts contained no traces of water, the recent Clementine mission suggested that small, frozen pockets of water ice (remnants of water-rich comet impacts) may be embedded unmelted in the permanently shadowed regions of the lunar crust. Although the pockets are thought to be small, the overall amount of water was suggested to be quite significant - one billion cubic meters, or an amount the size of Lake Erie. The presence of usable quantities of water on the Moon would be an important factor in rendering lunar habitation cost-effective, since transporting water (or hydrogen and oxygen) from Earth would be prohibitively expensive. Compared to that of the Earth, the Moon has a very small magnetic field. While some of the Moon's magnetism is thought to be intrinsic (such as a strip of the lunar crust called the Rima Sirsalis), collision with other celestial bodies might have imparted some of the Moon's magnetic properties. Indeed, a long-standing question in planetary science is whether an airless solar system body, such as the Moon, can obtain magnetism from impact processes such as comets and asteroids. Magnetic measurements can also supply information about the size and electrical conductivity of the lunar core -- evidence that will help scientists better understand the Moon's origins. For instance, if the core contains more magnetic elements (such as iron) than the Earth, then the impact theory loses some credibility (although there are alternate explanations for why the lunar core might contain less iron). Blanketed atop the Moon's crust is a dusty outer rock layer called regolith. Both the crust and regolith are unevenly distributed over the entire Moon. The crust ranges from 38 miles (60 km) on the near side to 63 miles (100 km) on the far side. The regolith varies from 10 to 16 feet (3 to 5 meters) in the maria to 33 to 66 feet (10 to 20 meters) in the highlands. Scientists think that such asymmetry of the lunar crust most likely accounts for the Moon's off-set center of mass. Crustal asymmetry may also explain differences in lunar terrain, such as the dominance of smooth rock (maria) on the near side of the Moon. The Moon has a relatively insignificant and tenuous atmosphere. One source of this atmosphere is outgasing - the release of gases, for instance radon, which originate deep within the Moon's interior. Another important source of gases is the solar wind, which is briefly captured by the Moon's gravity.
The Moon in mythThe Moon has figured prominently in various mythologies and folk beliefs. The numerous lunar deities are often female such as the Greek goddesses Selene and Artemis, their Roman equivalents Luna and Diana or the Thracian Bendis. However males are also found, such as Nanna or Sin of the Mesopotamians, Thoth of the Egyptians and the Japanese god Susanowo, along with Isil[?] in J. R. R. Tolkien's invented Middle-earth mythology.The term lunacy[?] is derived from Luna because of the folk belief in the Moon as a cause of periodic insanity. Folklore also stated that lycanthropes such as werewolves and weretigers[?], mythical creatures capable of changing form between human and beast, drew their power from the Moon and would change into their bestial form during the full Moon.
Observation of the MoonBy what can only be a truly extraordinary coincidence, the apparent size of the Moon as seen from the Earth is almost exactly the same as the apparent size of the Sun, so that total solar eclipses are possible where the Moon almost completely covers the Sun and the solar corona becomes visible to the naked eye[?].
Moon surface (magnify) Various lighter and darker colored areas create the patterns seen by different cultures as the Man in the Moon, the rabbit and the buffalo, amongst others. Craters and mountain chains are also prominent lunar features. The dark and relatively featureless lunar plains are called maria, latin for seas, since they were believed by ancient astronomers to be water-filled seas. The lighter-colored highlands are called terrae.
See also: Lunar phase.
The exploration of the MoonApollo 17 astronaut Harrison Schmitt standing next to boulder at Taurus-Littrow during third EVA. (magnify)
Humans first landed on the Moon on July 20, 1969 as the culmination of a Cold War-inspired space race between Russia and America. The first astronaut on the Moon was Neil Armstrong, captain of Apollo 11. The last man to stand on the Moon was scientist Harrison Schmitt, who as part of Apollo 17 walked on the Moon in December 1972. The European Space Agency and China both have plans to launch probes to explore the Moon in the near future. European spacecraft Smart 1 is scheduled for liftoff in mid-July 2003. The probe will be testing a new form of propulsion, an ion thruster. It will survey the lunar environment and create an X-ray map of the Moon. [2] (http://news.bbc.co.uk/2/hi/science/nature/2818551.stm) China has expressed ambitious plans for exploring the Moon and is investigating the prospect of lunar mining, specifically looking for the isotope Helium-3 for use as an energy source on Earth. [3] (http://space.com/missionlaunches/china-moon-030304.html) See also:
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