Past research proposals

Brief summary
This project aims to identify, for the first time, potentially prebiotic chemical pathways that could have led to ancestral archaeal lipids.  Archaeal lipids were likely one of the main components of the last universal common ancestor’s membrane, implying an ancient and potentially abiotic origin. Yet, prebiotic chemical pathways to archaeal lipids are unknown. Inspired by Nature, yet constrained by prebiotic plausibility and environmental conditions, we will explore the chemistry that led to ancestral archaeal lipids on primordial Earth. This work will, in turn, inform our search for environments conducive to (Archaea-like) lipid synthesis on other potentially habitable planets. planetary crust, seen to increase during Earth’s history due to the presence of complex life.

Importance of the area of research concerned
Lipid membranes are essential for all cells to maintain their integrity and individuality. Lipid membranes are also key in differentiating the domains of life. In Archaea, lipids are made of branched isoprenoid units linked to sn-glycerol-1-phosphate via ether bonds; in Bacteria and Eukarya, lipids are made of linear fatty acids linked to sn-glycerol-3-phosphate via ester bonds. This dichotomy in membrane lipid composition, known as the lipid divide, is hypothesized to have appeared early in the evolutionary timeline. Still, the lipid nature of the last universal common ancestor’s cell membrane and the mechanisms that led to its differentiation in Bacteria and Archaea remain unexplored.

What will the student do?
The student will investigate a range of different substrates and pathways under prebiotically-plausible conditions, including alcohol condensation, aldehyde reductive alkylation and ester photoreduction. The student will design and develop novel synthetic methods to generate libraries of archaeal phospholipids using a combination of solution phase, membrane-templated and dry-state chemistries. The resulting lipids will be purified and characterized, and synthetic methods will be optimized to prepare large-scale lipid libraries. The self-assembly properties of synthetic archaeal lipids and their features will be evaluated by fluorescence spectroscopy, light and electron-microscopy. Additionally, encapsulated prebiotic reactions, such as RNA replication and protometabolic processes, will be investigated to better understand the chemistry of bioinspired systems.  The student will also have the opportunity to test photochemical processes in the lab of Paul Rimmer (Department of Physics), expert in prebiotic photochemistry, and to regularly interact with the group of Buzz Baum (MRC LMB), expert in the biochemistry of Archaea. 

References
Hargreaves W., Mulvihill S. and Deamer D. - Synthesis of phospholipids and membranes in prebiotic conditions. Nature 266, 78-80 (1977). https://doi.org/10.1038/266078a0
Bonfio C., Russell D.A., Green N.J., Mariani A. and Sutherland J.D. - Activation chemistry drives the emergence of functionalised protocells. Chem Sci. 11, 1068810697 (2020). https://doi.org/10.1039/D0SC04506C
Lloyd C.T., Iwig D.F., Wang B. et al. - Discovery, structure and mechanism of a tetraether lipid synthase. Nature 609, 197–203 (2022). https://doi.org/10.1038/s41586-022-05120-2 Releva

Requirements as to the educational background of candidates that would be suitable for the project
Due to the nature of the project an undergraduate degree in chemistry or biochemistry is required.

Brief summary
This project aims at assembling primitive cells capable of division in the absence of modern biochemical machinery. Our lab has so far focused on the ability of primitive lipids to organise in different lipid domains. We now aim to employ primitive coacervates to modulate the surface area-to-volume of primitive liposomes, ultimately leading to division. This project will provide:
i) an understanding on the molecular features that govern interactions between membrane-less and membrane-bound compartments,
ii) a library of coacervates able to affect the surface area-to-volume of liposomes
iii) optimised protocols for the spectroscopic characterisation and imaging of primitive cell models.

Importance of the area of research concerned
Throughout evolution, modern cells have developed sophisticated machinery to precisely divide their membrane-bound compartments and regulate them. Yet, the minimal set of cellular components available for primitive cells to drive their division is still unknown. This lack of understanding calls for fundamental studies seeking strategies for primitive cell division.

This project aims to address this knowledge gap by exploring the cooperative interactions between primitive compartments (i.e., membrane-bound and membrane-less compartments), and their impact on enzyme-free cellular division.

Our research will serve as a biochemical platform for probing the origin of cellular replication, and the principles leading to the emergence of living cells. Moreover, not only will this project explore the synergy between protocell models so far only considered antithetically. It will also offer a more complete picture of the transition from prebiotic chemistry to early life.

What will the student do?
The student will be able to develop biophysics and supramolecular chemistry skills, which can be applied to membrane-bound and membrane-less model compartments (i.e., liposomes and biomolecular condensates). Specifically, the student will investigate the compatibility of complex coacervates, made of short oligonucleotides and positively-charged peptides, and lipid membranes, composed of primitive lipids (e.g., medium-chain fatty acids, phosphatidic acids and more complex phospholipids). The student will design and develop real-time spectroscopy- and imaging-based protocols to study the  interactions between different primitive cell models. The project offers interactions with other groups across multiple departments, including Prof. Lorenzo Di Michele, Dr. Phil Holliger and Prof. Rosana Collepardo-Guevara.

References
Hargreaves W., Mulvihill S. and Deamer D. - Synthesis of phospholipids and membranes in prebiotic conditions. Nature 266, 78-80 (1977). https://doi.org/10.1038/266078a0
Bonfio C., Russell D.A., Green N.J., Mariani A. and Sutherland J.D. - Activation chemistry drives the emergence of functionalised protocells. Chem Sci. 11, 1068810697 (2020). https://doi.org/10.1039/D0SC04506C
Lloyd C.T., Iwig D.F., Wang B. et al. - Discovery, structure and mechanism of a tetraether lipid synthase. Nature 609, 197–203 (2022). https://doi.org/10.1038/s41586-022-05120-2 Releva

Requirements as to the educational background of candidates that would be suitable for the project
Due to the nature of the project, an undergraduate degree in chemistry or biochemistry is required. The student should have an interest in supramolecular or biophysical chemistry, or artificial cell design and development.

Brief summary
Probing exogeology and signatures of biology in planetary material accreted by white dwarfs. Bulk abundances of planetary material seen in the atmospheres of some white dwarfs indicate geological process, including notably core-mantle-crustal differentiation. Key elemental species such as Fe, Ca, Si, Mg indicate the nature of the bodies. Trace species such as Li, Ni, Cr, Mn, P will be used to probe in further detail the evolutionary state of the material. In particular, the project will assess the ability of white dwarfs to probe the P content of planetary crust, seen to increase during Earth’s history due to the presence of complex life.

Importance of the area of research concerned
Although complex life clearly exists on Earth, the exact pathway to its existence is yet to be fully understood. Exoplanets provide the perfect opportunity to study what happened in our history that provided a safe haven for life. 

Although we now detect many rocky exoplanets, planetary material in the atmospheres of white dwarfs provides a unique means to probe the geological evolution of such planets. Spectroscopy reveals the bulk elemental composition of exoplanets, including Ca, Mg, Fe, P, C, S, Ni, Li etc. White dwarfs provide clear evidence of iron-core and crustal formation. 

This project focuses on the crustal reservoir as a unique probe of the geological conditions required for life. The project will investigate what can be uncovered by white dwarf observations, including potential signatures of the presence of biology. For example, the continental crust’s bulk Phosphorus (P) underwent a 3-fold enrichment following the evolution of animal life on Earth. 

What will the student do?
The project will be split into two parts: firstly analysing the range of elemental abundances available from white dwarfs presented in the literature, including objects such as NLTT 43806, which show evidence for the accretion of crustal material. Secondly making predictions for future observations with the capacity to detect particular geochemical signatures, including those related to the presence of biology. 

The student will create forward models predicting the composition of crustal material, based on various initial conditions and geochemical scenarios. These will be incorporated into existing models that aim to find the most likely explanation for the elemental abundances seen in white dwarf atmospheres, based on Bayesian analysis. The models will be used to determine an observational strategy best suited to exploring the evolution of crustal material. 

Strong numerical and computational skills, most likely from a physics, maths or geosciences background would be an advantage.

References
Walton C.~R., Hao J., Huang F., Jenner F.~E., Williams H., Zerkle A.~L., Lipp A., et al., 2023, Evolution of the crustal phosphorus reservoir, SciA, 9, eade6923. doi:10.1126/sciadv.ade6923
Buchan A.~M., Bonsor A., Shorttle O., Wade J., Harrison J., Noack L., Koester D., 2022, Planets or asteroids? A geochemical method to constrain the masses of White Dwarf pollutants, MNRAS, 510, 3512. doi:10.1093/mnras/stab3624
Jura M., Klein B., Xu S., Young E.~D., 2014, A Pilot Search for Evidence of Extrasolar Earth-analog Plate Tectonics, ApJL, 791, L29. doi:10.1088/2041-8205/791/2/L29

Requirements as to the educational background of candidates that would be suitable for the project
Strong numerical and computational skills, most likely from a physics, maths or geosciences background.

Brief summary
The project aims to test a new idea for interferometric wavelength calibration of EPRV spectrographs by building a prototype system and testing it in the laboratory. The new idea uses a broadband light source to illuminate the spectrograph through a Fourier-transform spectrograph (FTS) arrangement. Fourier analysis of the spectra seen for different values of the optical path difference in the FTS will allow high-precision measurement of the spectral response of each pixel.

Importance of the area of research concerned
The detection of ``Earth twins'' – rocky planets orbiting at radii of order 1au around solar-type stars – will be one of the major stepping-stones in our search for life in the Universe. One of the most promising avenues to make these detections is to use a spectrograph to detect the minute changes in the Doppler shift of the spectrum of the parent star caused by the orbiting planet. To extend existing Doppler techniques to the detection of an Earth twin requires extreme wavelength precision – the shifts in wavelength of the stellar spectral lines correspond to much less than a thousandth of the width of a pixel on the detector in the spectrograph. This research addresses the problem of accurately mapping the wavelengths of every pixel in a spectrograph at this level of precision.  

What will the student do?
The student will build a Michelson interferometer in the laboratory and use this to feed light into a test spectrograph. They will develop software in Python to control the interferometer and to analyse the data from the interferometer and the spectrograph. The student will use the results of this analysis to determine how well the system works and recommend future improvements to the system design.

References
Zhao, Lily L., David W. Hogg, Megan Bedell, and Debra A. Fischer. ‘Excalibur: A Nonparametric, Hierarchical Wavelength Calibration Method for a Precision Spectrograph’. The Astronomical Journal 161, no. 2 (January 2021): 80. https://doi.org/10.3847/1538-3881/abd105.

Charsley, Jake M., Richard A. McCracken, Derryck T. Reid, Grzegorz Kowzan, Piotr Maslowski, Ansgar Reiners, and Philipp Huke. ‘Comparison of Astrophysical Laser Frequency Combs with Respect to the Requirements of HIRES’. In Proc. SPIE, 10329:103290Y. International Society for Optics and Photonics, 2017. https://doi.org/10.1117/12.2271846.

Thompson, Samantha J., Didier Queloz, Isabelle Baraffe, Martyn Brake, Andrey Dolgopolov, Martin Fisher, Michel Fleury, et al. ‘HARPS3 for a Roboticized Isaac Newton Telescope’. In Proc. SPIE, 9908:99086F. International Society for Optics and Photonics, 2016. https://doi.org/10.1117/12.2232111.
 

Requirements as to the educational background of candidates that would be suitable for the project
This project requires a degree in Physics or related discipline. It would suit students with a background in optics, computer control of hardware, and data analysis.

Brief summary
Discovering signs of ancient extra-terrestrial life requires not only habitable paleoenvironments, but a subset of those where preservation of biosignatures was likely. Earth’s mudrock archive is a highly productive repository of fossil material, but it underwent step-changes in composition and mineralogy due to the evolution of bioturbation and land plants. The mudrock record predating these will be investigated to identify where different mud types (variable clay composition and physical attributes) were deposited in ‘source-to-sink' linked environments (i.e., from mountains, through rivers, to sea) when there was only a nascent microbial biosphere, potentially analogous to other planets.

Importance of the area of research concerned
Mudrocks could be key in the search for ancient extra-terrestrial life. Often deposited in habitable environments, their lithification is also suited for preserving biosignatures. Our understanding of mudrock is biased towards modern Earth, where biosphere influences are profound. To capitalize the potential of extra-terrestrial mudrock we need to understand Earth’s mudrocks from before the widespread establishment of life. The 1.5-billion-year-old Belt Supergroup is a natural laboratory recording mudrock-forming processes prior to multicellular life. Modern sedimentological investigation will 1) characterise environments that were a cradle for nascent microbial life, and 2) identify how mud transport and deposition operated before multicellular life, permitting comparisons to see how planetary environments can be shaped by life. Samples will be subjected to analyses of their clay minerals, utilizing cutting-edge electron imaging. These efforts will show which environments saw the deposition of mudrocks with high clay contents, identifying analogous astrobiological targets for recovering biosignatures.

What will the student do?
The Belt Supergroup of the NW USA is a widespread rock unit recording deposition in linked environments from mountain sources, through river conduits, to sinks in ancient lakes and seas.  The unit dates from before the advent of multicellular life and is overdue a sedimentological field investigation identifying different architectural styles of mudrock across these environments, framed as an analogue for similar environments on other planets. Fieldwork will allow the student to undertake this and collect contextualized samples. The student will conduct a state-of-the-art petrographic analysis of the recovered samples to determine which environments host the most desirable clay assemblages for organic matter preservation. New techniques in automated scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) mineral mapping will assess how the clay mineral content varies between environments and which were most likely to retain organic matter through clay-organic bonding.

References
Han, S., Lӧhr, S.C., Abbott, A.N., Baldermann, A., Farkaš, J., McMahon, W., Milliken, K.L., Rafiei, M., Wheeler, C. and Owen, M., 2022. Earth system science applications of next-generation SEM-EDS automated mineral mapping. Frontiers in Earth Science, 10, p.956912.
McMahon, W.J. and Davies, N.S., 2018. Evolution of alluvial mudrock forced by early land plants. Science, 359(6379), pp.1022-1024.
Schieber, J., 1998. Possible indicators of microbial mat deposits in shales and sandstones: examples from the Mid-Proterozoic Belt Supergroup, Montana, USA. Sedimentary Geology, 120(1-4), pp.105-124.

Requirements as to the educational background of candidates that would be suitable for the project
The project is suited to a student with a background in Earth Sciences, Geology or a related subject.

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: 

1. 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. 
2. 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. 
3. 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. 
4. Measure the efficiency of detrital, chemical, and viscous magnetisation processes in these sediments as a function of grain size and grain-grain interactions. 
5. 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). 

Brief summary
Earth’s history of rock weathering is written in the isotopic compositions of its oceans.  Oxygen isotopes in natural waters exchange with minerals during the low temperature weathering of rocks and during the high temperature exchange at mid-ocean ridge hydrothermal vents.  The oxygen isotope composition of seawater therefore provides a measure of how much water-rock reaction has occurred at low temperature (during weathering) and high temperature.  Seawater oxygen isotopic composition is therefore providing key information on Earth’s climate regulation mechanism.  In this project we will make novel oxygen isotope measurements of marine carbonates to reconstruct Earth’s climate regulation. 

Importance of the area of research concerned
Earth’s habitable and inhabited state is remarkable not only because of the events that led to it growing to just the right size, and endowed with just the right amount of water, carbon, and sulfur to get life started. But, because it has also managed to maintain its habitability for over 4 billion years.  This climate homeostasis, in the face of a major change in solar luminosity over that time and various cataclysms (impacts, snowball Earth events, large igneous province eruptions), suggests powerful stabilising climate feedbacks are built into the system.  Understanding these feedbacks is central to mapping the habitability of planetary systems throughout the galaxy.  In this project we will investigate how the central hypothesised mechanism for how this climate stability has been achieved on Earth, silicate weathering, has operated.  Focussing specifically on reconstructing where on the planet weathering has taken place to provide this climate stabilisation. 

What will the student do?

The student will perform oxygen triple isotope and clumped isotope analyses of brachiopod carbonate (over the Phanerozoic) and well-preserved sedimentary carbonates from the pre-Cambrian.  These measurements will be performed in the Department of Earth Science’s laser spectroscopy lab and in the Godwin laboratory.  Samples will be collected, prepared, digested, and analysed, and there is scope for individuals with interest in method development.   

Modelling of Earth’s coupled water and carbon cycles will be performed to interpret the data.   

References

• Walker, Hays, and Kasting, 1981. A negative feedback mechanism for the long-term stabilization of Earth’s surface temperature. Journal of Geophysical Research, 86:C10:9776—9782. 
• Pack and Herwartz, 2014. The triple oxygen isotope composition of the Earth mantle and understanding ∆17O variations in terrestrial rocks and minerals.  Earth and Planetary Science Letters, 390:138—145, doi: 10.1016/j.epsl.2014.01.017. 
• Krissansen-Totton and Catling, 2017, Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model. Nature Communications, doi: 10.1038/ncomms15423. 

Requirements as to the educational background of candidates that would be suitable for the project
This project would be suitable for students with experience of Earth Sciences and Chemistry/Geochemistry and a strong interest in laboratory geochemistry. 

Brief summary
There is huge uncertainty in the chemistry that occurred on early-Earth and other planets, and understanding this is one of the keys to understanding the formation of life from prebiotic conditions and assessing whether potential signatures of life seen on other planets are indeed correct and consistent with the chemistry present.

This project creates an automated framework for building reaction networks of relevant species and can generate data not known experimentally through accurate quantum chemical calculations, propagating any uncertainties in this to predicted outcomes., We will apply this to origin-of-life planetary conditions for the first time.

Importance of the area of research concerned
Atmospheric chemistry for present-day Earth contains well-benchmarked reaction networks allowing simulations of many chemical reactions. The environments on early-Earth and other planets are less well characterised, and for many species which do not readily occur on earth, estimates of thermodynamic and kinetic parameters are used, often off by many orders of magnitude.

This research will build a framework for the automatic creation of reaction networks, calculating the relevant quantities to sufficient accuracy, and including estimates of uncertainties, using quantum chemical methods. For gas phase species, these methods give high accuracy.  For condensed-phase species, the lower accuracy of automated methods will be supplemented by state-of-the-art calculations.
We will benchmark this for present-day Earth and experimentally-measured networks used in industrial applications and simulating air quality.

We will then use the networks to simulate early-Earth, Venus, and relevant exo-planet chemistries as these become better established.

What will the student do?
The student will build a python software framework to interface existing quantum chemistry software which calculates thermodynamic and kinetic quantities of relevance.  This framework will also include (and mine) any experimental databases for these quantities, and cross-validate them with computed values.

There are already existing networks, and processes for species generation which can be used to generate reaction networks, but the project may also explore filling-in holes and extending uncharacterised regions of such networks.

Initially the framework will focus on gaseous species, but will be extended to solvated or adsorbed species, where the uncertainties and calculations methods are far from automated, and significant work will be needed in designing interfaces, and collaboration with other specialists in chemistry who work in such areas.

With the generated networks and data the student will investigate and evaluate the plausibility of existing and potential hypotheses for planetary prebiotic chemistries.

References
M. Liu, A. Grinberg Dana, M.S. Johnson, M.J. Goldman, A. Jocher, A.M. Payne, C.A. Grambow, K. Han, N.W. Yee, E.J. Mazeau, K. Blondal, R.H. West, C.F. Goldsmith, W.H. Green. Reaction Mechanism Generator v3.0: Advances in Automatic Mechanism Generation, Journal of Chemical Information and Modeling 61, 2686-2696 (2021).

S. Sharma, A. Arya, R. Cruz and H. J. Cleaves II. Automated Exploration of Prebiotic Chemical Reaction Space: Progress and Perspectives, Life 11 1140-1–19 (2021).

A. Pérez-Villa, F. Pietrucci, A. M. Saitta. Prebiotic chemistry and origins of life research with atomistic computer simulations, Phys. Life Rev. 34–35, 105-135 (2020).

Requirements as to the educational background of candidates that would be suitable for the project
Undergraduates in Chemistry, Physics, Earth Sciences, Natural Sciences, and Chemical Engineering would be most suitable, though those some mathematical and programming background from biological sciences could also be suitable.

Brief summary
This PhD project will seek to provide constraints for answering two central questions for origins research: 

• What molecules survive cometary impacts?  
• What happens to the molecules that don’t survive? 

The experimental part of this work will involve heating different molecules known to be present on comets and connected to prebiotic chemistry, to find out how long they survive as a function of temperature. 

The modelling part of this work will involve taking primordial cometary chemistry as the initial conditions for an impact simulation using an established chemical kinetics model. The model will be supplemented by the student’s own experimental results. 

Importance of the area of research concerned
Comets have long been invoked as a potential source of the prebiotic ingredients required for life’s origins (Chyba & Sagan 1992). Recent major results conflict with each other about the potential for molecules of prebiotic relevance to survive cometary impact (Todd+2020,Zellner+2020). 

The student will apply both experimental and theoretical tools to determine which of these results is correct, and more broadly to make predictions about cometary post-impact environments relevant for Earth, Mars and for exoplanets. These predictions will be of great utility for prebiotic chemists to inform the conditions of their experiments, and for future observations of exoplanet systems, where the prebiotic implications of these events can eventually provide predictions about the potential for a cometary origin of life in an exoplanetary context. 

What will the student do?
The successful PhD student will look at molecules of prebiotic interest: Amino acids, nucleotides, ribose-aminooxazoline, simple sugars, phospholipid precursors. The lifetimes of these molecules will be measured under anoxic conditions over a range of temperatures (100 deg C – 500 deg C), and with different other molecules likely to be present on a comet (H2O, CO2, CO, NH3, HCN, H2S, SO2). These measured lifetimes and yields of thermolysis products will be published. 

These results will also be incorporated by the student into a far more comprehensive chemical kinetics model, incorporating hundreds of molecules and thousands of reactions, to predict the complex chemistry that is predicted to arise from cometary impacts.   

References

• Chyba, C. and Sagan, C., 1992. Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life. Nature, 355(6356), 125 
• Todd, Z.R. and Öberg, K.I., 2020. Cometary delivery of hydrogen cyanide to the early Earth. Astrobiology, 20(9), 1109 
• Zellner, N.E., McCaffrey, V.P. and Butler, J.H., 2020. Cometary glycolaldehyde as a source of pre-RNA molecules. Astrobiology, 20(11), 1377 

Requirements as to the educational background of candidates that would be suitable for the project
The successful candidate should have a background in Engineering, Physics or a closely related discipline. 

Brief summary
Whereas meteorites often contain diverse fragments from the same meteorite group, it is rare for meteorites to contain material belonging to different meteorite groups. Kaidun, a ‘meteorite collection in one stone’ [1. 2], contains many diverse meteorite types including rare aqueously altered, enstatite chondrites and alkaline igneous clasts, preserving a record of collisions between a differentiated planetesimal/planet and the evolution and alteration of primitive inner/outer solar system material. This project will characterise the nature, number and chemistry of the Kaidun lithologies with a view to understanding how interactions between inner and outer solar system primitive asteroids and differentiated planets influenced planetary habitability.

Importance of the area of research concerned
Collisions between planetary precursor meteorites characterised the evolution of our solar system, determining the chemistry and likely habitability of the terrestrial planets. However, direct records of these chaotic cosmic events are rarely preserved, limiting our understanding of their role in the development of habitable terrestrial planets and exoplanets.  

Meteorites provide the only direct record of early solar system events and permit a glimpse of the material central to planetary origins and the delivery of life-essential water/volatiles to planetary bodies. The Kaidun meteorite is an exceptional melange of  altered ordinary, enstatite and carbonaceous chondritic meteorite fragments with rare igneous clasts and preserves a unique record of early solar system mixing and collisions. This project will explore the origins and chemistry of Kaidun’s meteorite clasts, using this meteorite as a natural laboratory to constrain the role that solar system dynamics and planetary collisions played in the creation of habitable terrestrial planets. 

What will the student do?

Using SEM and clean geochemistry facilities at Cambridge and The OU, the student will undertake a petrographic and isotopic characterisation of Kaidun and address the following questions: 

1. What brought Kaidun’s inner and outer solar system lithologies together: is Kaidun a record of the planetary migration events? Can we use Kaidun to constrain the nature and timing of these events and potentially volatile element delivery to terrestrial planets?  
2. No combination of meteorites convincingly reproduces the Earth’s geochemical signatures. Are the clasts in Kaidun identical to known meteorites or are they unique? If the latter, could they be the ‘missing building blocks’ of Earth?  
3. Kaidun’s asteroid must have interacted with a differentiated body, potentially originating from Mars’ moon Phobos. If a link can be established, Phobos (Kaidun) may have captured Martian fragments during impacts. Can these clasts therefore provide insights into early Mars and the evolution of its surface?  

References

[1] Macpherson, G. J., Mittlefehldt, D. W., Lipschutz, M. E., Clayton, R. N., Bullock, E. S., Ivanov, A. V., Mayeda, T. K. & Wang, M.-S. 2009. The Kaidun chondrite breccia: Petrology, oxygen isotopes, and trace element abundances. Geochimica et Cosmochimica Acta, 73, 5493-5511. 
[2] Zolensky, M. & Ivanov, A. 2003. The Kaidun microbreccia meteorite: A harvest from the inner and outer asteroid belt. Geochemistry, 63, 185-246. 
[3] Kuramoto, K., Kawakatsu, Y., Fujimoto, M., Araya, A., Barucci, M. A., Genda, H., Hirata, N., Ikeda, H., Imamura, T. & Helbert, J. 2022. Martian moons exploration MMX: sample return mission to Phobos elucidating formation processes of habitable planets. Earth, Planets and Space, 74, 12. 

Requirements as to the educational background of candidates that would be suitable for the project

This project will suit an enthusiastic and highly motivated individual, preferably with a degree in geoscience, cosmochemistry of planetary science, or someone with relevant laboratory experience.  

The student will be supported and mentored to undertake and disseminate cutting edge research in the internationally competitive field of meteoritics. This project will present an excellent opportunity for the candidate to gain extensive training and analytical skills in the area of extraterrestrial sample science and to work with some of our key collaborators nationally and abroad, including colleagues at The Open University and at the Johnson Space Centre, and position them competitively to participate in preparing for the Mars Moons Explorer mission, scheduled by JAXA to return material from the Martian moon Phobos from 2028 [3].  

Brief summary
This project will determine how the break-up of large asteroids influences the conditions on nearby planets and consider the consequences for their habitability. Such break-ups create objects with sizes from large boulders down to dust, which then undergo dynamical evolution, some of which then being accreted. That accretion in turn influences the planet’s atmosphere and affects its climate. This project will model both these processes – the evolution of the debris field and the effect on the atmosphere – as well as how such events may be evident in the geological record, and their consequence for habitability.
 
Importance of the area of research concerned
The evolution of life on Earth has been strongly influenced by interaction with exogenous material from elsewhere in the Solar system – that is, asteroids, comets and dust in the zodiacal cloud. For example, the mid-Ordovician ice age has been linked to dust accreted following the break-up of a large asteroid and the extinction of the dinosaurs to an impact event. The accretion of this dust by the Earth, and its bombardment by larger bodies, was even more intense early on when life would have been developing, as evidenced by cratering on the Moon. The bright exozodiacal dust disks found around nearby particularly young stars show that these processes must also be occurring on exoplanets. It is thus important to determine the effect that this delivery of exogenous material may have had on the conditions on potentially habitable planets, and so its effect on the development and evolution of life.

What will the student do?
The project has 4 objectives: (1) develop a model with 3 distinct interdisciplinary components: (i) a dynamical model for the delivery to a planet of dust and asteroid-sized fragments following a collision, (ii) consider geological processes for the potential to recognise such events in the geological record, (iii) model how the planet’s climate is affected by accretion of this material. (2) Apply this to the asteroid break-up linked to both of the Earth’s geological record and climate to constrain any free parameters and to consider the viability of ice age triggering. (3) Consider how asteroid break-ups would have affected the Earth’s climate and geological record throughout its entire history, including the intense bombardment of early times. (4) Consider the implications of asteroid break-ups in extrasolar systems on their habitable plane

References
Archibald et al., 2020, GMD, 13, 1223
Schmitz et al. 2019, Sci. Adv., 5, 9, eaax4184
Rigley & Wyatt 2020, MNRAS, 497, 1143
Walton et al. 2024, Nature Astronomy, 8, 556 

Requirements as to the educational background of candidates that would be suitable for the project
For such an interdisciplinary project we do not expect to find a student with experience in all aspects of the project, so this is not required and the project would be tailored to accommodate the student’s interests/skills. The project would for example be suitable for a numerically-minded Earth Science or Atmospheric Chemistry student, or for an (Astro)physics student with broad interests/background.

Background 

The astrochemical formation of molecules is a highly active field of research and a fundamental step in the development of the chemistry necessary for life in the Universe. A wide range of molecules have now been identified in space [McGuire 2022, ApJS, 259, 30], which typically form through heterogeneous processes on grain surfaces.  Graphitic materials and silicates are relevant, but ice, in the form of amorphous solid water (ASW) is the most important substrate. 

Sophisticated astrochemical network models have been constructed to simulate the molecular formation processes that combine individual atoms then molecules on these surfaces, but such models are typically limited by knowledge of the underlying physical processes on the grains (adsorption, desorption, diffusion) [Cuppen, Astrochemistry, Space Sci. Rev. (2017)].  

Recent and ongoing laboratory based experiments have provided parameters for adsorption and desorption [Hama and  Watanabe, Chem. Rev. 113, 8783 (2013)] but very crude assumptions have been needed to provide the diffusion parameters that are needed in order to make progress.  There is little validation of such assumptions. 

Research Context 

The astrochemistry community has established that new tools are required to provide the diffusion parameters required for progress in this important field [Roadmap for Astrochemical Diffusion Studies, April 2024].  Helium Spin-Echo (HeSE), a technique developed by the Cambridge Surface Physics group, provides the perfect laboratory based technique to supply that information [Tamtögl, Nat. Comms. 12, 3120 (2021)]. To date, the method has been applied to a wide range of technological systems, including the metal surfaces generally associated with heterogeneous catalysis, and a range of 2d materials, but never astrochemically relevant systems. 

The astrochemistry community (notably including Lamberts, Walsh and Ligterink) have recently reached out to PI Jardine in the Cambridge Surface Physics group to address this challenge; the aim of this proposal is to exploit the HeSE technique to address this challenge alongside that community. 

Research Proposal 

The overarching aim of the PhD project is to provide diffusion information relevant to the astrophysical community, which will enable new astrochemical network models to be developed and confidence in existing models to be improved. 

The PhD will focus on gathering experimental data on various systems, starting with simple molecules on graphitic surfaces, then progressing to diffusion on the more complex ASW surface.  Since ASW structures vary, there will be an emphasis on developing methods to grow consistent materials in discussion with other laboratory based ASW experiments, before studying molecular diffusion.  Some instrument development may be required to achieve the low surface temperatures needed.  Similarly, given the level of sophistication of spin-echo data, analysis of the measurements will require molecular dynamics simulations, as well as development of methods for interpreting transport on amorphous surfaces. 

There will be active collaboration with the wider astrochemistry community throughout the project, to optimise experimental design and in order to exploit the resulting measurements. 

Project Summary

Prebiotic Chemistry, Geochemistry, Molecular Evolution Sulfur has long been thought to play a key role in prebiotic chemistry, largely due to its versatile oxidation states. In particular, reduced sulfur has been implicated in several prebiotic reactions, including the syntheses of amino acids, high energy phosphates, and several others. Although oxidised sulfur is thought to have been supplied to surficial environments as volcanic SO2, the sources of reduced sulfur and their transformations in prebiotic aquatic systems are poorly understood. I aim to investigate the origins and fate of reduced sulfur in aqueous environments on the early Earth. The aim is to identify key sources of reduced sulfur, characterise the origin and formation pathway of key activating agents such as thiocyanogen, and investigate the formation of catalytically-active minerals such as greigite. Initially, I will focus on volcanic S from atmospheric sources and the anoxic dissolution of sulfide minerals in water; using both theory and experiments to constrain the rates and pathways of aqueous reduced sulfur in systems intended to be analogous to potential “lake” environments on primitive Earth. I will investigate transformations as a function of temperature, atmosphere, evaporation-rehydration cycles and UV light. The goal is to investigate under what conditions and rates critical components such as thiocyanogen, may accumulate in pathways compatible with other prebiotic feedstocks.

Importance of the area of research concerned 

Prebiotic synthesis studies have shown that reduced sulfur is a critical component for the formation of several molecular building blocks for life. However, the geochemical sources of reduced sulfur are not well constrained. The results from this project will place constraints on the natural environments and processes that may have promoted the efficient and high-yielding synthesis and/or polymerisation of molecular building blocks on Early Earth.
 

What the student will actually do? 

This project will involve a comprehensive investigation of likely sources of reduced sulfur to aquatic systems, including atmospheric sources, volcanic sources, and geochemical sources driven by mineral transformations. The student will explore the fate and reactivity of reduced sulfur and its propensity to drive key geochemical and prebiotic reactions, through laboratory experimentation in oxygen-free systems, and in the presence/absence of UV light and other minerals which may act as catalytic surfaces. The aqueous concentrations of S-bearing compounds and the evolution of solids will be tracked, and results integrated in to a numerical model documenting concentration changes through time.

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.
 

References

• 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).
• Ranjan, S., Todd, Z. R., Sutherland, J. D. & Sasselov, D. D. Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry. Astrobiology 18, 1023–1040 (2018).
• Xu, J. et al. Photochemical reductive homologation of hydrogen cyanide using sulfite and ferrocyanide. Chemical Communications 54, 5566–5569 (2018).