Like kids throwing rocks in a pond, scientists just can't stop throwing things at the Moon. They've been doing it for half a century -- and it's all in the name of science.
Their projectiles are spacecraft and used-up rocket stages. The impacts gouge craters that can be big enough to hold a small office building.
A few of the impacts were accidents; craft that were designed to land softly on the Moon instead rammed into it at full speed. But most of them have been intentional.
In the early 1960s, for example, a series of Ranger spacecraft hit the Moon at about 6,000 miles an hour. They were America's first crack at reaching the Moon, and they snapped pictures of the lunar landscape as they plunged in.
Later, the boosters that carried Apollo astronauts to the Moon slammed into the surface to create "moonquakes." Instruments that the astronauts left on the surface measured the quakes, providing important information about the Moon's structure and composition.
And just last year, a spent rocket stage and a probe plunged into a crater near the Moon's south pole. The impacts blasted up plumes of dust that contained particles of frozen water -- confirming that ice does exist on the Moon.
The craters gouged by these impacts are too small to see from Earth. But you can see the Moon itself tonight. It rises in mid-evening, with the bright golden planet Saturn above it, and the star Spica to its lower left.
Script by Damond Benningfield, Copyright 2010
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