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Our Changing View of the Moon

History Corrected by 400-year-old Moon Map
The first drawing of the Moon through a telescope, dated July 26, 1609, by Thomas Harriot. This crude but historic sketch roughly delineates the terminator, the line that marks the boundary between day and night on the lunar surface. The original image is a little more than 15 cm across. The dark patches correspond to Mare Crisium (at the top), Mare Tranquilitatis and Mare Foecunditatis.
(Image: © © Lord Egremont)

The moon, so bright and large in the sky compared to othercelestial objects, has captured the attention of humans at least since the dawnof consciousness. Over these eras, mankind's view of the moon has evolved, fromthe more mystical image of it as a god, to the thought it was covered in seasand vegetation. Most recently, it's been viewed as a dry and dusty wasteland.

Recent findingsof water on the lunar surface could spur yet another shift in the way we seeour orbiting companion.

The moon appears in early art thousands of years ago,showing that early man was as enthralled by its eerie glow as laterphilosophers and scientists.

The moon, like the sun and the five planets visible to thenaked eye, was wrapped into the mythology of many ancient cultures, and considereda deity by some ? to the Egyptians it was Thoth, to the Greeks, Artemis, and tothe Hindus, Chandra.

Artemis was the twin sister of the sun god Apollo, and inHellenic tradition she held sway over childbirth, fertility and the hunt. Stagswere sacred to Artemis, and in many myths, she punished or killed those whoharmed them, such as the warrior Agamemnon.

Thoth was portrayed as a wise counselor who solved manydisputes and was also credited by the Egyptians as the inventor of writing andthe 365-day calendar.

The Hindus explained lunar (and solar) eclipses with Rahuthe snake, who swallowed the celestial orbs, making them go dark.

The moon was the basis of several ancient calendars and usedin determining astrological happenings. The cycle of the moon's waxing andwaning was tracked by many cultures and helped give rise to the modern month(the rough time it takes to go from full moon to new moon and back again), aswell the name of the second day of the week, Monday.

The moon haseven been blamed for some of the darker forces of human nature, such astemporary insanity. The term lunatic (and "loony") comes from theLatin name for the moon and many criminal and insane behaviors were once blamedon the presence of a full moon.

The full moon was also thought to transform afflicted humansinto fearsome werewolves, a more recent mythological creature most common inEuropean tales.

Full moons and lunar eclipses were also seen by somecultures as bad omens. When Christopher Columbus was stranded for a year onwhat is now Jamaica, during his fourth voyage to the New World, he intimidatedthe islands natives by correctly predicting a lunar eclipse.

The Man in theMoon ? an imaginary figure of a human, face, head or body ? has also longbeen a legend associated with the moon, and is still a feature spotted bychildren today. In the most commonly-recognized form in the West, the man's eyesare Mare Imbrium and Mare Serenitatis, its nose is Sinus Aestuum, and its openmouth is Mare Nubium and Mare Cognitum. In many European traditions, the figureis a man banished to the moon for some crime ? to some Christians, he is Cain,who murdered his brother Abel. To the Norse, he was Man?, who pulled the moonacross the sky, while the ancient Chinese saw the figure of a rabbit poundingmedicine.

Since Aristotle, the prevailing school of thought held thatthe heavens were more perfect than the Earth and therefore all celestialbodies, including the moon, were perfectly smooth spheres.

Galileo Galilei challenged this notion when he trained histelescope on Earth's satellite and sketched its surface. As he wrote in his1610 treatise The Starry Messenger, Galileo saw that the moon's surface was infact rough and rocky with dark, flat, low-lying regions and brighter highlands.(Though Englishman Thomas Harriot is actually credited with the firstmaps of the lunar surface.)

Early astronomers could see the light and dark areas of themoon, and though the former were continents, while the dark regions were seas.It was even though well into the 19th century that the moon had vegetation and possiblyeven moon beings.

No astronomers ever believed the notion that has entered popculture that the moon is made of green cheese. The phrase comes from an oldproverb that makes fun of the overly-credulous, namely those that see thereflection of the moon in the water and think it is a wheel of green (or young)cheese.

The craters covering the lunar surface were not widelyrecognized to be the results of impacts until well into the 20th century.Astronomer and geologist Eugene Shoemaker brought the principles of geology tothe study of the moon

Telescopic observations of the moon continued over thecenturies, but scientists were left with only the limited view theirEarth-bound perspective could provide.

Apollo answers

Once the era of rocket-powered space travel was ushered in,scientists could get information from a much closer vantage point.

Satellites sent up into space took more and better picturesof the lunar surface. In 1959, the Soviet Union's Luna 3 probe gave mankindit's first look at the far side of the moon.

But even with this better view, the moon was still somethingthat most thought of as a distant body in the sky, untouchable to man.

The Apollo landings changed all that and gave humanity it'sfirst up-close look at the lunar surface. The 12 Apollo astronauts that landedon the moon photographed, sampled and explored the gray, dusty terrain.

All told, these missions brought back to Earth about 840pounds (381 kg) of lunar rocks, which scientists zapped and examined to learnmore about the moon's makeup.

With the Apollo missions, "we answered so manyfundamental questions," said planetary geologist Larry Taylor of the Universityof Tennessee, Knoxville.

From these missions, scientists learned that the dark lunarmaria (Latin for "seas") were never actually seas, as was thought bythe ancient astronomers, but instead were composed of basalts, a type ofvolcanic rock. The brighter highlands though turned out to be made of themineral plagioclase feldspar, a common rock-building mineral on the Earth aswell.

The astronauts' experience also showed that the lunarenvironment was as "hostile as can be," Taylor said, with temperaturessoaring during the day and plummeting again at night, as well as "a bettervacuum than we can do in our labs" here on Earth.

The possibility of life existing on the moon held eventhrough the first moon landing. The Apollo 11 astronauts were quarantined forseveral days to make sure they hadn't brought back any germs from the moon orspace.

Understanding what the moon was made of also helpedscientists develop a theory for howit formed. The leading theory now: The collision of a Mars-sized objectwith the Earth broke off chunks of molten material that eventually coalescedand cooled into the moon.

"And that was really revolutionary," Taylor said.

Before the collision theory began to hold sway, otherexplanations for the moon's formation included fission of the Earth bycentrifugal forces (the severed chunk leaving behind a large basin, usuallynamed as the Pacific Ocean); capture of the moon after it formed elsewhere andwandered into the Earth's neighborhood; and formation at the same time as theEarth from the primordial accretion disk around the sun.

With the end of the Apollo program, interest in the moontapered off until more recent missions.

The new view

The science and understanding that came out of the Apolloprogram painted the moon as a long-dead, static body, and interest shifted toother destinations in our solar system, particularly Mars, with its enticingprospect as a suitable habitat for alien life.

The United States finally returned to the moon with theClementine spacecraft in 1994 and the Lunar Prospector in 1998. LunarProspector turned up interesting signals that seemed to indicate the presenceof hydrogen near the lunar poles ? a possible sign of water trapped inpermanently shadowed craters where scientists had suspected it could exist.

To further investigate the prospect of frozen water in polarcold traps, NASA developed and launched the Lunar Reconnaissance Orbiter (LRO)and its partner LCROSS impactor. LRO's mission is to map the lunar surface,while LCROSS slams into one of the polar craters to see if the ejecta debrisshows signs of the water ice.

But much to everyone's surprise, it was not LRO and LCROSSthat first turned up definitive signs of lunar water, it was a NASA-builtinstrument on India's Chandrayaan-1 satellite, along with the Cassini and DeepImpact spacecraft.

These probes detected the signatureof molecular water stuck to the surface of the planet ? how it got thereand exactly what form it is in is still a mystery ? in very small quantities.

The unexpected discovery is "one of the biggestfindings post-Apollo," said Ray Arvidson. It could also be "a shot inthe arm to lunar exploration," renewing interest in both robotic and humanmissions to our satellite, he added.

But whatever future missions are planned, one thing iscertain: The existence of water on the moon changes the way we think about oursatellite. Instead of a dead, gray rock orbiting the Earth, "it's adynamic world in our backyard," said Jim Garvin, one that will help uslearn more about the solar system we live in.

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