Similarities and differences between the solar wind light noble gas compositions determined on Apollo 15 SWC foils and on NASA Genesis targets

Autor: Heinrich Baur, F. Bühler, Nadia Vogel, Rainer Wieler, Addi Bischoff, M. Horstmann, Veronika S. Heber, Peter Bochsler, A. Grimberg
Rok vydání: 2015
Předmět:
Zdroj: Meteoritics and Planetary Science
ISSN: 1945-5100
1086-9379
DOI: 10.1111/maps.12503
Popis: We compare the solar wind (SW) He Ne and Ar compositions collected during the Apollo Solar Wind Composition (SWC) experiments (1969 1972; Al Pt foils) and the Genesis mission (2002 2004; so called DOS targets considered here). While published SW Ne 20/Ne 22 and Ar 36/Ar 38 ratios of both data sets agree differences exist in the He 4/He 3 He 4/Ne 20 and Ne 20/Ar 36 ratios. However Ne 20/Ar 36 ratios from Apollo 16 Pt foils exclusively adopted as SW values by the SWC team are consistent with the Genesis results. We investigate if the differences indicate a variability of the SW over the course of about 30 yr or systematic biases of the two data sets which were collected in different environments and measured several decades apart in different laboratories (University of Bern; ETH Zurich). New measurements of Apollo 15 SWC aluminum foils in Zurich generally agree with the original measurements performed in Bern. Zurich samples show slightly lower He 4 concentrations suggesting a few percent of diffusive loss of He 4 during storage of the foils. A 3 difference between the He isotopic ratios measured in Bern and in Zurich possibly represents an analytical bias between the laboratories. The low SW He 4/Ne 20 and Ne 20/Ar 36 ratios in Apollo 15 Al foils compared to Genesis data are consistent with a mixture of Genesis like SW and noble gases from small amounts of lunar dust. Our data suggest that the mean SW He Ne and Ar isotopic and elemental compositions have not significantly changed between the overall Apollo and Genesis mission collection periods.
Databáze: OpenAIRE
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