Magnetising the early Earth
Lead Supervisor: Richard Harrison, Department of Earth Sciences
Co-supervisor: Nick Tosca, Department of Earth Sciences
Brief summary
Is strong magnetisation an essential ingredient in the origin of life? A definitive answer to this question would have major implications for the search for life on other planets –narrowing our search to planetary bodies with a stable magnetic field. The CISS effect provides a link between strongly magnetised sediments and homochirality. Sediments are magnetised through a range of natural processes (grain rotation, in-situ grain growth, thermal activation, shock or lightning), most leading to weak or spatially inhomogeneous magnetisation incapable of producing homochirality without additional amplification. Here we will test a range of potential amplification mechanisms that could plausibly operate under early Earth conditions.
Importance of the area of research concerned
The origin of homochirality, or the selection of one of two mirror-image forms (or enantiomers) of the same molecule, has persisted as a fundamental problem in the origin of life. A recent breakthrough in this field has been made with the discovery of the chiral-induced-spin-selectivity (CISS) effect, which describes a strong enantioselective interaction between ribose-aminooxazoline (RAO) and magnetite surfaces, which induces high-yielding chiral selectivity at a critical point in viable prebiotic reaction networks.1,2 Magnetite may be produced in anoxic alkaline lake settings on the prebiotic Earth and Mars3, but for the CISS effect to operate, the magnetite-rich sediment must be strongly magnetised under the influence of a weak planetary magnetic field and/or be capable of being strongly magnetised by interaction with the RAO molecules. The combination of physical and chemical processes that could have produced sufficiently strongly magnetised sediments are poorly constrained. This project would aim to address this question through a combined experimental and modelling approaches and test the plausibility of the CISS effect as the origin of biological homochirality.
What will the student do?
The student will study the physical and chemical processes that could have created strong magnetisation in early Earth sediments. This will involve:
- Laboratory experiments to grow magnetic minerals (magnetite, greigite) from aqueous solutions under anoxic conditions in the presence of silicate minerals, to mimic the formation of sediments on the early Earth.
- Control the experimental conditions to influence the grain size distribution of magnetic minerals, yielding grains in the critical size window (80-100 nm) where theory predicts amplification of remanence could be significant.
- Study the interaction of magnetic grains with each other and with the silicate phases (silica, clays) to understand the plausible spatial distributions of magnetic grains in the sediment and the effect of interactions on amplification.
- Measure the efficiency of detrital, chemical, and viscous magnetisation processes in these sediments as a function of grain size and grain-grain interactions.
- Use micromagnetic modelling and thermal activation theory to predict levels of sedimentary magnetic amplification under plausible early Earth conditions.
References
- Ozturk, S. F. & Sasselov, D. D. On the origins of life’s homochirality: Inducing enantiomeric excess with spin-polarized electrons. Proc National Acad Sci 119, e2204765119 (2022).
- 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. Sci. Adv. 9, eadg8274 (2023).
- Tosca, N. J., Ahmed, I. A. M., Tutolo, B. M., Ashpitel, A. & Hurowitz, J. A. Magnetite Authigenesis and the Warming of Early Mars. Nat Geosci 11, 635–639 (2018).
Requirements as to the educational background of candidates that would be suitable for the project
General background in the physical sciences (e.g. physics, chemistry, materials science, Earth sciences, planetary sciences).
Applying
You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.