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.

Very Long Baseline Interferometry (VLBI) involves observing radio sources with astronomy telescopes, from which very accurate estimates of distances between telescopes and estimates of Earth rotation can be made. Recently, a software program was developed at Swinburne University (Victoria) to correlate astronomic VLBI observations - which is a very significant improvement over convential correlation and provides Australian researchers with considerable independence. This PhD program will involve continuing the development of the software correlator so that it can be applied to geodetic VLBI observations as well. Once this can be done, exciting new opportunities will become available - such as observing GPS satellites using VLBI instruments, analysing for the first time the data from the new VLBI installations in Western Australia and the Northern Territory (to be commissioned in 2008). The student will be involved in developing and enhancing software, analysing VLBI data and integrating the VLBI observations to GPS satellites into existing geodetic software packages. The student will be supervised jointly by Steven Tingay (Swinburn) and Paul Tregoning (ANU).

We don't know yet what new results such research is going to uncover ...... come and find out!

This topic is a subject of very active research in the geophysical community and was exploited in a recent science-fiction motion picture 'The Core' (although the scientific facts in the movie were almost entirely wrongly represented). Differential rotation of the inner core with respect to the rest of the planet was first suggested from numerical simulations of the geodynamo in 1995. Since then, seismological studies aiming to detect differential rotation of the inner core using temporal changes in seismic waveforms were mostly controversial, and often subjected to criticism (the title above was taken from a publication in Science). One reason for scrutinising seismological data is a very likely inadequate resolution to resolve small temporal changes in inner core properties. This project will explore a unique dataset from Australian seismic stations to address the above issue. A highly motivated student with a background in geophysics, physics, astronomy or mathematics will find the project challenging and satisfying. Please contact the supervisor directly at hrvoje@rses.anu.edu.au for more information.