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Ironing out prebiotic environments on the early Earth
Lead Supervisor: Nicholas Tosca, Earth Sciences
Co-supervisor: Ziwei Liu, Earth Sciences; Clancy Jiang, Earth Sciences; Paul Rimmer, Cavendish

Brief summary
Fe is critical to prebiotic synthesis but its availability in prebiotic environments is virtually unknown. This project will focus on the reactions that regulate Fe availability beginning with controls on dilute water chemistry, and then alkaline systems. The project will experimentally characterise the nucleation and growth kinetics of Fe(II)/Fe(III)-(hydr)oxide, phosphate and carbonate phases under prebiotically-relevant conditions, and will investigate interactions between inorganic materials and organic feedstocks/ products to identify inorganic-organic feedback processes. The experimental constraints will be integrated into numerical models that predict Fe concentration across a range of parameters, and identify optimal conditions compatible with prebiotic synthesis.

Importance of the area of research concerned
Current scenarios for the origins of life on Earth depend on the synthesis of key molecular building blocks - ribonucleotides, amino acids, and lipids. The synthesis of these compounds requires UV light, high phosphate, and high cyanide concentrations, but iron (Fe) is also critical to this chemistry; it combines with cyanide to form ferrocyanide complexes which mediate photochemical HCN reduction, and it may have formed the Fe-mineral magnetite, which has been implicated in the origins of homochirality (the selection of one of two mirror image molecular forms). Alkaline lakes are thought to have promoted such chemistry, but the behaviour of Fe in such settings is unknown because the modern Earth’s O2-rich atmosphere prevents it from accumulating in alkaline lake waters, and few experiments have examined its behaviour in prebiotic systems. A detailed understanding of Fe chemistry in alkaline lakes is therefore critical to connecting prebiotic chemistry with early Earth environments.

What will the student do?
The student will design and implement experiments to investigate controls on Fe availability in the Aqueous Geochemistry Laboratory in the Department of Earth Sciences. Experiments will involve in-situ monitoring of chemical composition and in-situ characterisation of the emergence and behaviour of solid materials through vibrational spectroscopy, X-ray diffraction, and electron microscopy. Experiments will investigate the role of UV light through collaboration with Dr Rimmer (Cavendish). Kinetic analysis, and geochemical modelling will be used to examine distribution of inorganic and organic products as a function of time and with varying environmental parameters.

Ozturk, S. F., Liu, Z., Sutherland, J. D. & Sasselov, D. D. Origin of biological homochirality by crystallization of an RNA precursor on a magnetic surface. Science Advances 9, eadg8274 (2023). 

Brady, M. P., Tostevin, R. & Tosca, N. J. Marine phosphate availability and the chemical origins of life on Earth. Nature Communications 13, 5162 (2022). 

Xu, J. et al. Photochemical reductive homologation of hydrogen cyanide using sulfite and ferrocyanide. Chemical Communications 54, 5566–5569 (2018). 

Requirements as to the educational background of candidates that would be suitable for the project
Most suitable undergraduate subject areas: chemistry and/or Earth sciences.

You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.