Preliminary Genesis Bulk Solar Wind Ar, Kr, and Xe Abundances in Comparison to Young Lunar Regolith and Solar Photosphere Data

Introduction: A major objective of GENESIS is to constrain the present day solar wind (SW) Ar, Kr, and Xe isotopic and elemental compositions by direct measurements of SW irradiated artificial samples [1]. Due to the low abundances of heavy noble gases in the SW, until now these compositions could only be inferred from regolith samples which were irradiated by the SW over large time spans [e.g., 2-4]. Analysis of Genesis samples is more challenging due to the small amounts of heavy noble gases accumulated in the targets during the only 853 days of SW exposure. On the other hand, the interpretation of Genesis data should be more straightforward than that of regolith samples due to the lack of further major noble gas reservoirs and better controlled fractionation processes during ion implantation in Genesis targets. Here, our preliminary new Genesis SW data will first be compared to data from “young” lunar regolith samples (having acquired SW during the last ≤100 Ma) [3-5]. It has been postulated [3-5] that such samples carry elementally and isotopically unfractionated “modern” SW Ar, Kr, and Xe at the very grain surfaces. This can now be tested with the new Genesis data. Second, the Genesis data will be compared with the solar photospheric heavy noble gas composition. This is of major importance in order to better understand and quantify fractionation processes between the Sun and the SW, e.g., the so-called FIP-fractionation (see below). This will finally serve to better constrain solar system elemental and isotopic abundances, which in turn allow ruling on the composition of the solar nebula.