Water on the Moon May Pose Problems for Lunar Telescopes

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NEW YORK — The presence of water on the Moon may be a boon for future manned bases, but new research suggests it also might put a major crimp in plans for ambitious telescopes on the lunar surface.

As the molecules of Moon water vaporize in sunlight, the scattering process could heavily distort observations taken by any telescopes built there, the new study found.

“Last year, scientists discovered a fine dew of water covering the Moon,” said Zhao Hua, an astronomer with the Chinese Academy of Sciences. “This water vaporizes in sunlight and is then broken down by ultraviolet radiation, forming hydrogen and hydroxyl molecules.”

The researchers found that those lunar hydroxyl molecules may be present in substantially more quantities than previously thought — levels high enough to pose an interference or contamination risk to any telescopes on the Moon’s surface.

The research was presented Sept. 21 at the European Planetary Science Congress in Rome.

The Moon’s potential as a site for building astronomical observatories has been a concept discussed since the space race between the United States and former Soviet Union to send humans to the lunar surface.

A lunar-based telescope could have several advantages over ground-based telescopes on Earth, including a cloudless sky and low seismic activity, researchers said.

Initially, scientists thought the Moon’s surface was bone dry. But that all changed in 2009 when observations by several spacecraft from NASA, Japan and India returned proof of the chemical signature for water, as well as water ice at the Moon’s poles.

Millions of tons of water ice have been discovered in permanently shadowed craters at the Moon’s north pole. One probe found water ice hidden in craters at the lunar south pole, while other observations found that water molecules were present in small quantities on the Moon’s surface.

About 1 ton of the top layer of the lunar surface would hold about 0.95 liters of water, researchers said at the time. The findings have been encouraging for space officials hoping to tap the Moon water resource for future manned missions, but their impact for other lunar science efforts is just beginning to be understood.

The research also has important implications for the upcoming lunar missions, including China’s unmanned Chang’e 3 Moon lander mission, which is scheduled to launch in 2013.

The lander is expected to operate on the Moon’s sunlit surface and be equipped with a solar-powered ultraviolet telescope. China’s second lunar probe, Chang’e 2, is due to launch later this year.

“At certain ultraviolet wavelengths, hydroxyl molecules cause a particular kind of scattering where photons are absorbed and rapidly re-emitted,” Zhao said. “Our calculations suggest that this scattering will contaminate observations by sunlit telescopes.”

Still, the far side of the Moon could be an ideal site for radio astronomy, the researchers said.

With its face pointed away from Earth, the Moon’s far side is permanently shielded against interference from our planet, and radio observations — unlike optical telescopes — would not be affected by the higher lunar hydroxyl levels, they said.