The isotopic composition of neon emitted in solar flares and trapped in lunar soil minerals

Closed system etching of lunar soil samples and stepwise mass spectrometric analysis of the He, Ne, and Ar released has been developed. This noble gas release technique prevents isotopic and elemental fractionation occurring in stepwise heating. Measurements on one pyroxene and two plagioclase separates reveal the presence of trapped noble gases emitted during solar flares (SEP Ne) besides the solar wind, confirming earlier indications for such a component. Solar wind Ne and SEP Ne are isotopically different. The currently best estimate for the composition of SEP Ne is: 20-Ne 22Ne = 11.1 ± 0.2, 21-Ne/22Ne ≤ 0.029. The 20Ne/22Ne ratio reported here is within error limits equal to Ne-C found in meteorites but agrees at best marginally with the respective value measured by satellite borne instruments. SEP Ne found in lunar soils is not identical with ''planetary Ne'', as has been suggested. Only weak evidence that SEP Ar may be isotopically different from solar wind Ar was found