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.

A new approach for the internally consistent modelling of the equation-of state and elastic properties of minerals under the extreme pressure-temperature conditions promises to revolutionise the interpretation of seismological models for the Earth’s interior. The new method has recently been bench-tested on a diverse range of experimental data for magnesium oxide (Kennett & Jackson, Phys. Earth. Planet. Interiors, 2009). Now, there is an opportunity for the involvement of a Ph. B. / Honours/ M. Sc. student in the systematic application of this approach to experimental data, including local measurements of the pressure and temperature dependence of elastic wave speeds, for the upper-mantle mineral olivine and its high-pressure polymorphs wadsleyite and ringwoodite.

Mantle plumes carry heat upwards from a thermal boundary layer at the bottom of the mantle, and the thermal boundary layer is formed by heat conducting out of the core. Plumes thus help to cool the core. The efficiency with which plumes remove heat is debated and needs to be clarified. The project would be to use an existing numerical code to explore different parameters that control the plume and to compare the resulting plume with observational constraints. Some programming experience would be required.