Profile of the moon
What it is: Earth's only natural satellite and the only astronomical body other than Earth ever visited by humans.
Location: About 238,900 238,855 miles from Earth, or the equivalent of driving a car around 142 days at 70 mph.
Age: About 4.5 billion years old, the same as the rest of our solar system; is believed to have formed when Earth collided with a planet-sized object and the resulting debris accumulated.
Appearance: Its surface is pitted with craters because it has no protective atmosphere. Light and dark areas suggest a Man in the Moon. The light areas are lunar highlands and ancient crust. The newer dark areas, called maria, are impact basins that were filled with dark lava between 2.5 billion and 4 billion years ago.
Movement: Rotates in sync with the Earth, so we always see the same face. The moon orbits the Earth about every four weeks.
What it lacks: An atmosphere. The moon's sky is always black and the stars are always visible. The moon also has no moving tectonic plates or active volcanoes.
More than 70 moon missions have been carried out by various countries. The last U.S. trek was the Lunar Prospector, which orbited the moon from January 1998 to July 1999 and found strong evidence of ice in both poles.
Twelve astronauts have walked on the moon; they brought back a total of 842 pounds of moon rock and soil. Most of the rock is at the Lunar Sample Laboratory Facility at the Johnson Space Center in Houston.
The moon's weak gravity makes it easy to move around. A 200-pound person on Earth would weigh only 34 pounds on the moon.
Neil Armstrong, the first person to walk on the moon, apparently flubbed the famous line he had prepared for his step to the surface. He was heard to say, “That's one small step for man, one giant leap for mankind.” He said later he meant to say (and may have said), "That's one small step for a man…” In 2006, an Australian entrepreneur reported his analysis of an audio recording found the missing “a.” But earlier this month, a British linguist and an author said their study of the original NASA recordings found Armstrong omitted the “a.”
Italian astronomer Galileo wrote the first scientific description of the moon based on telescope observations. He told of a rough, mountainous surface in 1609. Before then, the moon was believed to be smooth.
Many moon craters are named for famous scientists. One is named after Nicolaus Copernicus, a Polish astronomer who realized in the 1500s that planets orbit the sun.
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