Rapidly evolving composition of nebular infall recorded by magnesium isotopes in refractory inclusions
Haoyu Li1, Ren T C Marquez1, Gerrit Budde1,2
1The Isotoparium, Division of Geological and Planetary Sciences, Caltech, Pasadena, CA 91125.
Abstract:
The 26Al-26Mg systematics in calcium-aluminum-rich inclusions (CAIs)-the oldest known Solar System solids-has traditionally been used to provide high-resolution temporal constraints on the early Solar System evolution. More recently, the study of variations in the initial Mg isotope composition has emerged as a means to probe for potential compositional heterogeneity in the nascent solar nebula. Here, we report high-precision magnesium isotope data for a collection of 19 CAIs that captures the diversity of refractory inclusions. The data reveal widespread Mg isotope heterogeneity prior to 26Al decay, covering a large range from -0.285 to +0.088‰. Combined with literature data, the distribution of Mg isotope heterogeneity in CAIs forms a continuum and no longer defines distinct populations. Our findings therefore suggest a continuous CAI formation process that captured a rapid temporal change in the composition of infalling material from the parental molecular cloud of the Solar System.
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