Source Of Moon's Magnetism Found

From Yahoo News/Space.com:

Moon rocks delivered to Earth by Apollo astronauts held a mystery that has plagued scientists since the 1970s: Why were the lunar rocks magnetic?

Earth's rotating, iron core produces the planet's magnetic field. But the moon does not have such a setup.

Now, scientists at MIT think they have a solution. Some 4.2 billion years ago, the moon had a liquid core with a dynamo (like Earth's core today) that produced a strong magnetic field. The moon's magnetic field would have been about 1-50th as strong as Earth's is today, the researchers say.

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