July 9, 2008

Moon Rocks Contain Water

The general agreement about the Moon had been before that it was completely dry. No traces of water at all. And detailed research of the Moon rocks brought back by the Apollo astronauts seemed to completely confirm this agreement for more than 30 years. But new discoveries have showed that the Moon does contain a little bit  of water.

Image: Some of the volcanic glasses brought to Earth by the Apollo astronauts. Credit: NASA

The Formation of the Moon

The most widely accepted theory about the creation of the Moon involves an impact between a Mars-sized body, called Theia, and the Earth about 4.5 billion years ago. This impact is believed to have launched enough material into space which gradually coalesced into the Moon.

During this formation, most scientists believe that any water existing on the developing moon would have been vaporized into space. Because of this, many think that water has not existed at all on the Earth's satellite. However, this idea may be changed by a research team from Brown University, whose findings were published in the July 10 issue of Nature.

The Research Team

Assistant professor of geological sciences at Brown University, Alberto Saal, has led a team that has discovered evidence for water on the Moon. Analyzing the lunar volcanic glasses, small beads collected by the Apollo 15 mission, they have found minute traces of water. Previously, these rocks were thoroughly searched, but evidence of water did not appear.

But Saal and his team decided to use a technique developed by Erik Hauri from the Carnegie Institution for Science: secondary mass ion spectrometry. Earlier techniques could detect water in the lunar rocks to about 50 ppm (parts per million), but this technique could detect to about 5 ppm. This led to the detection of water in the glass beads.

Water in the Beads

The glass beads were created from small droplets of magma that has come from fire fountains more than 3 billion years ago. The team believes that almost all of the water vapor in the magma disappeared as gas into space right after it came out.

They studied the beads to make sure that they originated from the fire fountains and not fromt he impact of Theia. Saal's team also had to check that the beads were not contaminated by outside factors, like hydrogen from the solar wind.

After the team analyzed the beads, they found that they contained 46 ppm of water. Knowing that most of the water had evaporated during the eruption of the fire fountains, they estimated that pre-eruption magma contained up to 750 ppm of water.

Origin of the Water

So this finding generates a new question: Where did the water on the Moon come from? There are right now two possible answers to this question. Water either did not completely vaporize into space during the formation of the Moon, or came later from the outside, such as from meteorites. This new discovery certainly has sparked new interest in the existing Moon rocks that were brought by the Apollo astronauts to Earth.

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