July 9, 2008
Scientists Find Evidence Of Water On The Moon
Scientists have decided that evidence collected from the surface of the Moon almost 40 years ago shows that water existed there since its infancy.
Small green and orange pebble-like beads collected decades ago from the Moon's surface were used to analyze the lunar sand samples that are thought to be some 3 billion years of age.The researchers believe these samples could support evidence that water persists in the shadowed craters of the Moon's surface and that it is native to the moon as opposed to being carried there by comets.
Alberto Saal, assistant professor of geological sciences at Brown University believes that the water was contained in magmas erupted from fire fountains onto the surface of the Moon more than 3 billion years ago. About 95 percent of the water vapor from the magma was lost to space during this eruptive "degassing".
He said that if the Moon's volcanoes released 95 percent of their water, it was possible that traces of water vapor may have drifted toward the cold poles of the Moon, where they may remain as ice in permanently shadowed craters.
He noted that several lunar missions have found just such evidence.
A technique called secondary ion mass spectrometry or SIMS, can detect minute amounts of elements in samples.
Erik Hauri of the Carnegie Institution for Science in Washington developed the technique along with his research team to find evidence of water in the Earth's molten mantle.
"Then one day I said, 'Look, why don't we go and try it on the Moon glass?'" Saal said.
It took them three years to convince NASA to fund a study of the samples brought back by astronauts during the Apollo missions in the 1970s.
After careful analysis of 40 of the tiny glass beads, which were broken apart, they discovered evidence that overturned decades of conventional wisdom that the moon is dry.
Saal, Hauri and colleagues did not find water directly, but they did measure hydrogen, and it resembled the measurements they have done to detect hydrogen, and eventually water, in samples from Earth's mantle.
They found that the hydrogen in the sample vaporized during volcanic activity would be similar to lava spurts seen on Earth today.
"We looked at many factors over a wide range of cooling rates that would affect all the volatiles simultaneously and came up with the right mix," said James Van Orman, a former Carnegie researcher now at Case Western Reserve University.
Hauri said the findings suggest the possibility that the moon's interior might have had as much water as the Earth's upper mantle.
"It suggests that water was present within the Earth before the giant collision that formed the Moon," Saal said.
"That points to two possibilities: Water either was not completely vaporized in that collision or it was added a short time "“ less than 100 million years "“ afterward by volatiles introduced from the outside, such as with meteorites."
NASA plans to send its Lunar Reconnaissance Orbiter later this year to search for evidence of water ice at the Moon's south pole. If water is found, the researchers may have figured out the origin.
Saal and his research team's study was published in the July edition of the journal Nature.
Image Caption: Watery Glasses Researchers led by Brown geologist Alberto Saal analyzed lunar volcanic glasses, such these gathered by the Apollo 15 mission, and used a new analytic technique to detect water. The discovery strongly suggests that water has been a part of the Moon since its early existence "“ and perhaps since it was first created. Credit: NASA
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