Planetary Origins and Development

Scientists can now detect Earth-sized planets orbiting other stars far away in our Milky Way galaxy. Yet, many basic aspects of how planets first form, then develop and function are unknown or surprisingly uncertain. The research in this proposal will address some of the questions to which scientists seek answers in this fascinating area.

The subjects in which we work are called isotope cosmochemistry, petrology, rock physics and low temperature geochemistry. Four lead investigators with these different backgrounds will work together to address five big questions.

1. What processes generated the atoms from which our Solar System was built? Hydrogen and helium are mainly the product of the Big Bang 13.8 billion years ago. But what about all the heavier elements like calcium, titanium, chromium, nickel, zirconium, molybdenum or palladium? Since the 1950s there have been well accepted theories for how these heavier elements were synthesised in large stars. Now there is evidence these theories may be wrong. We will measure the proportions of the isotopes of these elements in some of the oldest material in the Solar System to test the new theories.

2. What processes govern the amount of volatile elements like tin in the terrestrial planets? We will perform experiments using a recently-built furnace to determine the relative losses and isotopic fractionation of such moderately volatile elements from molten asteroidal and planetary bodies. We will evaluate whether very early processes in the circumstellar disk were responsible or whether there were losses from large planetary volcanoes into space. This work may also tell us about the atmospheres of some hot exosolar planets.

3. How do metallic cores form and differentiate? The Earth like all terrestrial planets has an iron core. In the case of Earth it is partially liquid, so convects, generating a magnetic field. How do such cores form and then crystallise? We will measure isotopic variations in vanadium, chromium, nickel, molybdenum, palladium and tungsten in meteorites, which together with experiments, will provide new insights into core formation and crystallisation in early planetary embryos as well as larger objects. These are expected to also shed light on the nature of the Moon-forming impactor Theia.

4. How do rocky planetary interiors respond to orbital stresses? On Earth we are aware of tidal forces from the Moon that cause the interior of a planet to move. Shortly after the Moon formed it was very close to Earth - it would have occupied a third of the night sky! So the tidal forces would have been vastly bigger. Yet we do not know much about how a rocky planet responds to such huge stresses. We will conduct laboratory experiments to evaluate this.

5. How do planetary crusts influence atmospheric evolution? One of the most important aspects of the development of habitable worlds is the formation of an atmosphere. However, the release of one of the most important and simple of elements, hydrogen, is not well understood. There are ideas emerging from climate modelling and origins of life studies that we will test with new experimental and modelling investigations of hydrogen generation through the interactions between water and rock.

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 being realised because of technique developments in isotope geochemistry, including in the biomedical sciences. Recently, we published our first paper on zinc isotopes in breast cancer using some of the same techniques as we are deploying to study the Moon's origins. (See Project B in this proposal.)
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 mass spectrometers 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 (Oxford University Innovation), has recommended the further development of collaborative links with mass spectrometry equipment manufacturers such as Nu as a possible source of future commercialization.
In addition to this, in 2014 the University established Oxford Science Innovation with initial funding of >£300m from the private sector globally but including Wellcome. They, as well as STFC through the University's STFC Impact Acceleration Account, are providing support for the PI to build a robotic sample chemistry facility that, it is anticipated, will lead to commercialization opportunities. We expect that the broad applicability of existing and emerging isotope geochemistry techniques to be supported by this proposal will attract further 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, as well as funding substantial complementary research with one of the new co-Is (Tosca). 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. 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 (MNH) (>500,000 visitors/yr). The PI is on the Board of Visitors to the MNH, which reopened in 2014 after a year long refurbishment program.