The history of mixing nucleosynthetic components during formation of our Solar System

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All chemical elements heavier than lithium, that comprise the Earth and our Solar System, were produced by nuclear reactions in stars, and mixed during formation of the Solar System. It was once thought that that mixture once existed as a hot and almost homogeneous molecular cloud, and the minerals, planetesimals and planets formed during its cooling and gradual condensation and accretion.

That concept was overthrown by discovery of refractory materials (Ca-Al-rich inclusions and hibonite grains) containing isotopic anomalies that are incompatible with condensation from homogeneous 'bulk solar' gas. Existence of presolar grains with extreme isotopic compositions for many elements, and small but systematic differences in isotopic compositions of Mo, Cr, Ni, Ba and other elements between Earth, Mars, and meteorites from various asteroids demonstrates heterogeneity of the Solar System at scales from micron-sized minerals to planets.

The pattern of mixing, however, remains poorly understood. The student will explore the timing of mixing nucleosynthetic components and mechanisms of homogenisation by precise isotopic analysis of several elements containing isotopes produced in various stellar environments from selected meteorites, and by comparative modelling of mixing and mass-independent fractionation that can possibly mimic incomplete mixing.

The main emphasis can be given to either an analytical or a modelling part, depending on the talents and skills of the student.

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