Lunar finding doesn’t hold water

Only a few years ago, planetary scientists were excited by reports that shady craters at the moon’s poles might contain substantial amounts of ice. The hydrogen in frozen water could serve as rocket fuel for space explorers. But new radar findings may dampen earlier enthusiasm.

Using the 305-meter radio dish at Arecibo Observatory in Puerto Rico, researchers examined several craters at the moon’s poles. Compared with lunar soil, which absorbs radar signals, ice would produce a strong radar reflection. In the Nov. 13, 2003 Nature, Donald B. Campbell of Cornell University and his colleagues report seeing no such reflection.

According to the team, the finding counters that of the lunar-orbiting Clementine spacecraft, which gathered radar reflections indicating that a south-pole crater could contain ice (SN: 1/4/97, p. 11). A spectrometer aboard another craft revealed that the poles are rich in hydrogen (SN: 3/14/98, p. 166).

It’s still possible that amounts of ice too small to provide a clear radar signal lie within polar craters, says Paul Spudis of the Johns Hopkins Applied Physics Laboratory in Laurel, Md., who analyzed the 1994 Clementine data. The issue won’t be settled, he says, until a lander is sent to regions suspected of harboring ice.


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