Mg Isotopic Composition of the Solar Wind by SIMS Analysis of Genesis Targets

摘要

In order to deduce the isotopic compositions in theudsolar nebula of volatile elements, e.g., noble gases, O, and N, from analysesudof the solar wind (SW), we must understand the magnitude of mass-dependentudfractionation between the SW and the photosphere. With theudexception of evaporation effects in CAIs, mass-dependent fractionation ofudMg isotopes is small, as evidenced by Mg isotopic compositions ofudterrestrial igneous and meteoritic samples which agree within ~1‰ [1].udThus, if we assume that the "terrestrial" Mg isotopic composition is alsoudrepresentative of the solar photosphere, we can use measurements of theudSW captured by Genesis to test models of isotopic fractionation inudformation of SW. For example, if the inefficient Coulomb-drag model [2]udis correct, we would expect that the Mg isotopic composition in the SW isud~10‰ per amu [2] lighter than the terrestrial composition.ud