Water on Moon clouds plans for lunar astronomy

Space scientists from the Chinese Academy of Sciences have calculated that the scattering caused by molecules vaporised in sunlight could heavily distort observations from telescopes mounted on the Moon.

"Last year, scientists discovered a fine dew of water covering the Moon. This water vaporises in sunlight and is then broken down by ultraviolet radiation, forming hydrogen and hydroxyl molecules. We recalculated the amount of hydroxyl molecules that would be present in the lunar atmosphere and found that it could be two or three orders higher than previously thought," said Zhao Hua, who will be presenting results at the European Planetary Science Congress in Rome on Tuesday 21st September.

The research has particular implications for the Chinese Lunar lander, Chang'e-3, which is planned to be launched in 2013. An ultraviolet astronomical telescope will be installed on the Chang'e-3 lander, which will operate on the sunlit surface of the Moon, powered by solar panels.

These images from NASA's Moon Mineralogy Mapper on the Indian Space Research Organization's Chandrayaan-1 spacecraft show data for the hemisphere of the moon that faces Earth. The image on the left shows albedo, or the sunlight reflected from the surface of the moon. The image on the right shows where infrared light is absorbed in the characteristic manner that indicates the presence of water and hydroxyl molecules. That image shows that signature most strongly at the cool, high latitudes near the poles. The blue arrow indicates Goldschmidt crater, a large feldspar-rich region with a higher water and hydroxyl signature. Credit: ISRO/NASA/JPL-Caltech/Brown Univ.

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

The Moon's potential as a site for building astronomical observatories has been discussed since the era of the Space Race. Lunar-based telescopes could have several advantages over telescopes on Earth, including a cloudless sky and low seisimic activity.

The far-side of the Moon could be an ideal site for radio astronomy, being permanently shielded from interference from the Earth. Radio observations would not be affected by the higher hydroxyl levels.

Source: Europlanet
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