StarDate: July 22, 2009

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Ticker-tape parades and a White House dinner awaited the crew of Apollo 11 when it returned from the Moon 40 years ago. But first, the astronauts had to spend three weeks locked inside an airtight laboratory. There were fears that exotic "germs" might live on the Moon. If so, humans would have no resistance to them, and might suffer a plague.

The six Apollo Moon-landing missions found no evidence of life on the Moon, though -- now or in the past. But they did provide information about the life of the Moon itself.

Instruments left on the lunar surface found that the only "moonquakes" are caused by the pull of Earth's gravity. Instruments also revealed that the Moon consists of a thin crust surrounding a thick layer of solid rock, a thinner layer of warm "plastic" rock, and a small, iron-rich core.

Moonrocks helped scientists determine that the Moon probably formed when an object as big as Mars crashed into the newborn Earth. The collision vaporized much of our planet and spewed the hot gas into space, where it quickly cooled and coalesced to form the Moon.

Over the next billion years, asteroids punched holes in the Moon's crust, allowing molten lava to bubble to the surface. As the lava cooled it formed the dark lunar "seas." Since then, though, the Moon has been a quiet place, with no water, no atmosphere -- and no life -- to disturb its slumber.

The Apollo samples are still teaching us about the Moon's history. More about that tomorrow.

Script by Damond Benningfield, Copyright 2009

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