Lunar surface, isotope production

Whereas isotopes produced in the solid matter of meteorites or the lunar surface material remain at their production sites, isotopes produced mainly in the earth s atmosphere are separated according to the geochemical properties of the different elements. 

Studies Based on Isotope Production in Meteorites and on the Lunar Surface... 

The W/ W ratios of lunar rocks have been difficult to determine because there is significant W production via neutron-capture of Ta during prolonged cosmic-ray exposure of the lunar surface 30, 32). This problem has now been overcome by analyzing metals from lunar basalts 30). These metals contain no Ta and hence no cosmogenic W. Touboul et al. 33) obtained W isotope data for metals from a comprehensive set of lunar rocks and showed that probably all lunar samples have Sw values of 0. Hence, the lunar and terrestrial mantles have identical W isotope compositions. 

Masarik J, Nishiizumi K, Reedy RC (2001) Production rates of cosmogenic He, Ne, and Ne in ordinary chondrites and the lunar surface. Meteoritics Planet Sci 36 643-650 McCoy TJ, Keil K, Clayton RN, Mayeda TK, Bogard DD, Garrison DH, Wieler R (1997) A petrologic and isotopic study of lodranites evidence for early formation as partial melt residues from heterogeneous precursors. Geochim Cosmochim Acta 61 623-637... 

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