Planetary Origins and Development

Lead Research Organisation: University of Oxford
Department Name: Earth Sciences


The research in this proposal tries to answer questions about how our solar system and its reservoirs first formed. We are proposing to focus our efforts on the issue of how terrestrial planets acquired their metallic cores (the same cores that drive planetary magnetic fields). In the process we will also determine how the silicate Earth's budgets of metal loving elements like Ni originated. We will make comparisons between the differentiated planets and asteroids, Earth, Mars, Vesta and the angrite parent body on the one hand and the Moon on the other and use these data to better constrain lunar origins.

We use a combination of isotopic measurements using mass spectrometry, and experimental simulation at high pressures and temperatures. We have isotopic evidence that metallic cores of planets started forming very early; within the first million years or so of the Solar System's earliest objects, calcium aluminium refractory inclusions. These cores formed from molten rock created from accretional energy and, initially, radioactive decay. As metallic cores form they partition a variety of elements into the dense segregating metallic liquids partially removing these elements from the residual silicate planet. The degree of depletion and the magnitude of any associated isotopic fractionation will depend on the conditions under which these cores formed, in particular the pressure, temperature, oxygen fugacity and sulphur content. Therefore, by measuring the isotopic compositions of primitive meteorites and comparing them with those of samples of the silicate and metal portions of asteroids, Mars, Earth and the Moon one can deduce the environment under which different planetary objects first developed. To quantify these environments it is necessary to calibrate the isotopic and chemical effects with experimental determinations. We will focus our attention on vanadium, chromium, nickel, molybdenum, tungsten and, if time permits, ruthenium.

Planned Impact

Geochemistry (and isotope geochemistry in particular) is already having an enormous impact in scientific research across a range of disciplines. Furthermore, the potential for further advances in understanding is considerable because, thanks to new technology, we now can use isotopes much more effectively to explore a vast array of processes, from the point of view of timing, tracing and ambient conditions. Geochemistry has now become the single biggest discipline within Earth Sciences and provides much of the critical data and constraints for planetary sciences. Significant links to other fields are anticipated as a result of technique developments in isotope geochemistry, including in the life sciences.

As a discipline underpinned by very advanced instrumentation, isotope geochemical measurements are refined in collaboration between academia and private sector instrumentation companies. Oxford Earth Sciences has had a long and fruitful partnership with Nu Instruments, which was founded in 1995 to co-develop instrumentation with the Department. Today, Oxford Earth Sciences uses six Nu machines and there is a strong and continuing two-way flow of technology, staff and ideas which have resulted in jointly authored research publications, bilateral staff transfers (both secondment and permanent recruitment) and bespoke instrumentation.

Oxford University's Technology Transfer Office, Isis Innovation, has advised on the potential for knowledge exchange in this consolidated grant proposal and recommended the further development of collaborative links with mass spectrometry equipment manufacturers such as Nu as a possible source of future commercialization potential.

We expect that the broad applicability of existing and emerging isotope geochemistry techniques to be supported by this proposal will attract industrial interest in our research, leading to further funding from a range of industries. For example, the oil industry has long been interested in isotopic fractionation within transition metals, and a collaboration with one industrial partner in this area has already provided collateral support for activities funded under the original Planetary Origins and Development award from STFC. A further example of fruitful industrial collaboration seeded by STFC funding - led by co-I Wood - has been with Tata Steel, focusing on trace element partitioning to elucidate non-metallic inclusions in low-alloy steels. There is every reason to expect that, as the techniques develop over the tenure of this proposed consolidated grant, the new laboratory for isotope geochemistry at Oxford will form the focus for a number of such industry funded collaborations which would ultimately lead to knowledge and technology transfer to these industries.

The formation of the terrestrial planets also meets with widespread public fascination - research on the origin of the solar system addresses questions that the public want to see answered. The PI has long been engaged in radio and television broadcasting and is also involved in the promotion of solar system science in schools. A recent highlight (September 2013) has been a Royal Society scientific meeting convened by the PI, with the co-I (Wood) as a session chair. The PI appeared on the BBC R4 Today programme, as well as BBC Radio Scotland and BBC Five Live Sports to explain the fascination about the Moon's origins.

Oxford has both an effective press office (to deliver material for public consumption in the form of the Oxford Science blog, Itunes U podcasts, etc) and an enormously popular Museum of Natural History (>500,000 visitors/yr) to facilitate the communication of our science to the wider public. The Museum has just reopened (February 2014) after a year long refurbishment programme.


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Gall L (2017) Nickel isotopic composition of the mantle in Geochimica et Cosmochimica Acta

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Halliday A (2015) Treatise on Geophysics

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Hopkins S (2019) The vanadium isotopic composition of lunar basalts in Earth and Planetary Science Letters

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Horner TJ (2015) Persistence of deeply sourced iron in the Pacific Ocean. in Proceedings of the National Academy of Sciences of the United States of America

Description We have discovered that the chromium isotopic composition of the silicate Earth is chondritic contrary to the results reported in an earlier high profile paper by another group. This means that core formation has not fractionated the Cr isotopic composition which is not what is found for Si but is similar to what we have found for Mo and Ni.

We have discovered dramatic fractionations in Cr in iron meteorites resulting from fractional crystallisation of the metallic cores of planetary embryos. This is leading to new areas of research on core processes.
Exploitation Route Not clear at this stage but the high precision techniques used are of widespread value in environmental sciences
Sectors Environment

Description Science outreach. PI gave sold out talk on the Moon as part of the Oxford "Pint of Science" evenin in May 2017.
First Year Of Impact 2017
Sector Education,Leisure Activities, including Sports, Recreation and Tourism,Culture, Heritage, Museums and Collections,Other
Impact Types Cultural