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First conclusive signature for lunar uranium
Posted: June 29, 2009

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Robert C. Reedy, a senior scientist at the Tucson-based Planetary Science Institute, is mapping the Moon's surface elements using data gathered by an advanced gamma-ray spectrometer (GRS) that rode aboard the Japanese Kaguya spacecraft.

The data promise to show chemical elements on the Moon that have never been identified before, and Reedy and the Kaguya GRS team already have found uranium signatures in the data, an element not seen in previous Moon-mapping efforts.

The uranium results were recently announced in papers presented at the 40th Lunar and Planetary Conference and at the Proceedings of the International Workshop Advances in Cosmic Ray Science. The lead authors on those papers are Prof. Naoyuki Yamashita and Prof. Nobuyuki Hasebe respectively. Both are from Japan's Waseda University.

Earlier gamma-ray spectrometer maps from the Apollo and Lunar Prospector missions show a few of the Moon's chemical elements. But the maps constructed by Reedy and the Kaguya GRS team -- using data gathered by state-of-the-art, high-energy-resolution germanium detectors -- are extending the earlier results and improving our understanding of the Moon's surface composition.

In addition to uranium, the Kaguya GRS data also is showing clear signatures for thorium, potassium, oxygen, magnesium, silicon, calcium, titanium and iron.

Reedy and his colleagues are using measurements from the Kaguya lunar orbiter's GRS to construct high-quality maps of as many chemical elements as possible. Kaguya was launched in September 2007 and crashed into the Moon at the end of its mission on June 10 of this year.

"We've already gotten uranium results, which have never been reported before," Reedy said. "We're getting more new elements and refining and confirming results found on the old maps. Some of these comparisons are being done with lunar elemental maps made by a Lunar Prospector team headed by PSI senior scientist Tom Prettyman."

Reedy has been an official co-investigator on the Kaguya GRS team since 2007, and has received some support from the Japan Aerospace Exploration Agency (JAXA).

"Being selected as a co-investigator for a JAXA planetary mission is a great honor," Reedy said.

Reedy's continuing mapping work now is being funded for two years through NASA's SALMON program (Stand-Alone Missions of Opportunity).

"All of the work being funded is considerably improving our knowledge of the Moon's composition and its origin and evolution," Reedy said. It also will help scientists locate lunar resources and help with planning for future lunar missions, he added.

In addition to Reedy, the Kaguya GRS team includes Hasebe (the GRS principal investigator), Yamashita, and Yuzuru Karouji, of the Waseda University in Tokyo, Japan; and Claude d'Uston and Olivier Gasnault, of the Centre d'Etude Spatiale des Rayonnements in Toulouse, France.