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Apollo 15 green glass He-Ne-Ar signatures – In search for indigenous lunar noble gases

Füri, E. ; Zimmermann, L. ; Saal, A.E., Geochem. Persp. Let.

Apollo 15 green glass He-Ne-Ar signatures – In search for indigenous lunar noble gases

Füri, E. ; Zimmermann, L. ; Saal, A.E.

Geochemical Perspectives Letters, 2018, 8, 1-5

Abstract :

Identifying indigenous lunar noble gases in samples returned by the Apollo and Luna missions is highly challenging because contributions from the solar wind (SW) and/or cosmogenic nuclides have modified the noble gas signature of the regolith and rocks exposed to space at the lunar surface. Here we re-investigate the possible presence of indigenous noble gases in pyroclastic Apollo 15426 green glasses based on precise measurements of He-Ne-Ar isotopic compositions and abundances. The noble gas content of single glass beads varies by two orders of magnitude, indicating that they experienced highly variable irradiation histories as a result of intense regolith stirring by impact gardening. Four out of the twelve spherules stand out by having the highest He-Ne-Ar abundances and by releasing an isotopically ‘solar-like’ noble gas component at high temperatures. While a contribution from indigenous noble gases cannot be ruled out, the data are best accounted for by inward diffusion of, and equilibration with, SW-derived volatiles during prolonged space exposure.

Voir en ligne : http://dx.doi.org/10.7185/geochemle...




publié mardi 2 octobre 2018