Apollo Moon Rocks Challenge Lunar Water Theory: Scientific American - 0 views
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The discovery of "significant amounts" of water in moon rock samples collected by NASA's Apollo astronauts is challenging a longstanding theory about how the moon formed
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Since the Apollo era, scientists have thought the moon came to be after a Mars-size object smashed into Earth early in the planet's history, generating a ring of debris that slowly coalesced over millions of years
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That process, scientists have said, should have flung away the water-forming element hydrogen into space
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a new study suggests the accepted scenario is not possible given the amount of water found in moon rocks collected from the lunar surface in the early 1970s
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By "water," the researchers don't mean liquid water, but hydroxyl, a chemical that includes the hydrogen and oxygen ingredients of water.
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the impact scenario is the best formation scenario for the moon, but we need to reconcile the theory of hydrogen
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Past studies have suggested water-forming elements came to the moon from outside sources long after the moon's crust cooled
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The solar wind — a stream of particles emanating from the sun — as well as meteorites and comets were pegged as possible sources ofwater depositson the moon in recent studies
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Because they found hydroxyl deep inside each sampled rock, the scientists say they have eliminated the solar wind moon water explanation
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An impact from an asteroid or comet could push the hydrogen in further, but it would not be as pristine as the samples the researchers observed, because it would have melted from the heat of the asteroid collision
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Researchers probed samples from the late Apollo missions, including the famous "Genesis Rock" that was named for its advanced age of 4.5 billion years, about the same time the moon is thought to have formed
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Hui's research flies in the face of past analyses of Apollo rocks that found they were very dry, except for a small bit of water attributed to the rock containers leaking when they were returned to Earth
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older spectrometers had a sensitivity of around 50 parts per million (ppm), while his instruments were able to detect water at concentrations of about 6 ppm in anorthosites and 2.7 ppm in troctolites, which are both igneous rocks found in the moon's crust.