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Water World

July 17, 2013

Until a couple of decades ago, the subject of water on the Moon was as dead as the Moon itself — there didn’t seem to be a drop of water anywhere. Today, though, planetary scientists are jumping into the subject with all the vigor of children at a pool party. Not only are they finding water, they’re also studying its origins and what it can tell us about the evolution of the Moon and Earth.

A couple of months ago, a study reported that the water on the Moon is a chemical match for the water on Earth. That suggests that their water had a common origin.

The Moon likely was born in a “big whack” — a collision between Earth and another planet. The impact sprayed out material that coalesced to make the Moon.

Scientists have thought that the collision vaporized not only any water, but molecules of hydrogen as well — one of the chemical building blocks of water. That would have left the Moon high and dry. So any water on the Moon today must have been deposited there later — by comets, for example.

But a study of tiny amounts of water in moonrocks from two Apollo missions suggests otherwise. The water in these samples matches the water found on Earth. The researchers say the match probably means that some of Earth’s water survived the big whack — and was incorporated into the newly formed Moon.

Look for the Moon in the south as night falls. The orange star Antares is to its lower left, with the golden planet Saturn about the same distance to its upper right.


Script by Damond Benningfield, Copyright 2013

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