SSS 2009-09-24（在线收听）

For all you space buffs who like to keep track of where the water is, it looks like you can add our very own moon to your list. Because according to a trio of papers appearing in the journal Science, the lunar surface is wetter than we realized.

Forty years ago, Apollo astronauts brought a bunch of moon rocks back home. For the most part those samples showed no traces of water whatsoever. Those that seemed even the slightest bit moist were thought to have been contaminated by water from Earth—because the containers they were stored in turned out to be leaky.

But now scientists say they’ve spotted water right on the moon’s surface. Using instruments on three different spacecraft, the scientists detected the chemical signature of good old H2O. And they think the water springs from the moon itself. The lunar soil is nearly 50 percent oxygen, and the scientists think that hydrogen comes from the solar wind that pounds the moon’s surface.

Put the two together and you get wet. Not too wet, of course. There’s probably only about a quart of water in every ton of lunar soil. That’s dryer than the Sahara. But wetter than we thought.