Project EARTH-17-STFC-AH1

Accretion and Core Formation in the Inner Solar System

Supervisors: Prof Alex Halliday, Dr Jane Barling, Dr Waheed Akram and Dr Sara Russell (Natural History Museum)

This studentship will explore isotopic differences between basaltic achondrites, iron meteorites, lunar samples and chondrites.  The student will use these measurements to address the origin of the Moon-forming giant impactor planet Theia, as well as how metallic iron cores formed and crystallised in the inner Solar System.  Elements that are partitioned between metal and silicate are expected to undergo isotopic fractionation between the phases because of the differing stiffness of the bonds.  This has been demonstrated both theoretically and experimentally (e.g. Georg et al., 2007; Hin et al., 2013).  As such, isotopic measurements have the potential to provide powerful insights into the formation of differentiated asteroid-sized planetary embryos as well as larger objects like Mars, Earth and the Moon.  In practice, many of these elements, though depleted in the silicate Earth, are not as fractionated, relative to average Solar System, as expected, for reasons that are not well understood (Halliday, 2013; Bonnand et al., 2016; Liang et al., 2016; Gall et al., 2017).  It could be that the temperatures were higher than expected, the accreting material was different, or the conditions of core formation diverged from those that have been assumed.  Surprisingly large isotopic fractionations have been found within magmatic iron meteorites representing planetary core material however.

This studentship will involve studies of extra-terrestrial materials as well as some terrestrial samples and considerable isotope geochemistry laboratory work.  The student will receive training in a range of sampling methods from meteorites to igneous rock suites and volcanoes and will learn innovative mass spectrometry techniques.

This project will be funded by the Science and Technology Facilities Council (STFC).

How to apply:

Candidates should apply in the usual way via the University’s online admissions system here.

The deadline for applications is Friday 17 February 2017.

Suggested reading:

Bonnand, P., Williams, H.M., Parkinson, I.J., Wood, B.J. and Halliday, A.N. 2016 Stable chromium isotopic composition of meteorites and metal-silicate experiments: implication for fractionation during core formation. Earth Planet. Sci. Lett 435, 14-25.

Gall, L., Williams, H.M., Halliday, A.N. and Kerr, A.C. 2017 Nickel isotopic composition of the mantle Geochim. Cosmochim. Acta, 199, 196-209.

Georg, R. B., Halliday, A. N., Schauble, E. a., and Reynolds, B. C. 2007 Silicon in the Earth’s core. Nature, 447, 1102–1106.

Halliday, A.N. 2013 Small differences in sameness. Nature 497, 43-45.

Halliday A.N. 2014 The origin and earliest history of the Earth. In: Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, vol. 2, 149-211. Oxford: Elsevier.

Hin, R.C., Burkhardt, C., Schmidt, M.W., Bourdon, B. and Kleine, T. 2013 Experimental evidence for Mo isotope fractionation between metal and silicate liquids. Earth Planet. Sci. Lett. 379, 38-48.

Liang, Y-H., Halliday, A.N., Siebert, C., Fitton, J.G. Burton, K.W., Wang, K-L. and Harvey, J. 2017 Molybdenum isotope fractionation in the mantle Geochim. Cosmochim. Acta, 199, 91-111.