Is the moon too wet for astronomy? Chinese scientists have found evidence that our airless, dry-as-a-bone satellite actually contains enough water vapor to complicate the operations of some telescopes. In 2013, China plans to place a small ultraviolet observatory on the lunar surface. UV astronomy must be conducted in an airless environment—in Earth orbit, say, or on the moon—because water molecules in Earth's atmosphere absorb UV light. But at a presentation yesterday at the European Planetary Science Congress in Rome, researchers from the Chinese Academy of Sciences have found a hitch in the latter prospect. Chemical surveys taken from India's Chandrayaan-1 spacecraft have detected the presence of water vapor on the lunar surface (blue areas). Sunlight breaks down the water molecules, freeing individual hydrogen atoms, which can scatter incoming ultraviolet light and smear images. The effect is sufficient, the scientists have concluded, to distort images enough that UV astronomers with lunar ambitions may have to look elsewhere.
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