The global distribution of calcium on the Moon: Implications for high-Ca pyroxene in the eastern mare region

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The first unambiguous global distribution of Ca on the Moon has been revealed by the Kaguya Gamma-Ray Spectrometer. The observation of the 3737keV gamma rays from <SUP>40</SUP>Ca with a high energy resolution Ge detector, corrected for fast neutrons, improved greatly our confidence in these remote sensing data. While the derived Ca abundance generally confirms the mare-highland dichotomy, we found that the eastern mare regions such as Crisium, Nectaris, and Fecunditatis exhibit unexpected high Ca abundances. This may be explained by regional concentrations of high-Ca clinopyroxene. Our Ca map also shows that the lowest CaO abundance found in the returned samples (∼8wt%) may actually be common in Oceanus Procellarum, suggesting the possible sampling bias of Apollo and Luna missions. These observational results on Ca serve as a complementary criterion for better characterization of mare regions on the Moon.</P> <P><B>Highlights:</B></P> <P>► Global distribution of Ca on the Moon is derived from Kaguya GRS data. ► Observation by high precision Ge detector greatly improved confidence in measurement. ► Ca was found to be more abundant in the east mare region than in the west. ► Selective concentration of high-Ca pyroxene in the eastern mare region is implied. ► Ca provides a complementary criterion to characterize the lunar thermal history.</P>