Research proposals

2025-2026

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf

PI: Amy Bonsor, abonsor@ast.cam.ac.uk, Institute of Astronomy

Project 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. White dwarfs provide the key to interpreting planetary interior models in time for space missions such as PLATO to detect hundreds of rocky exoplanets.

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.

Spectroscopic follow-up of hundreds of newly identified white dwarfs from Gaia is revolutionizing the field of white dwarf planetary science.

What the student will actually do?
The project is a mixture of spectroscopic data, geochemical and planet formation models. White dwarfs should have pristine spectra, with only features from hydrogen or helium. A small sub-set display many more features. This project is about interpreting these features, using them to infer the composition of the planetary material in the atmosphere of the white dwarf. These compositions are then used, in a similar manner to meteorite data for the Solar System, to interpret the geology and history of the exoplanetary systems.

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.

References

Bonsor, A., 2024., White Dwarf Systems: the Composition of Exoplanets, Chapter for the 'Encyclopedia of Astrophysics' (Editor-in-Chief Ilya Mandel, Section Editor Dimitri Veras) doi:10.48550/arXiv.2409.13294
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

PI: Claudia Bonfio, cb2036@cam.ac.uk, Department of Biochemistry
Co-I: Edoardo Gianni, egianni@mrc-lmb.cam.ac.uk, MRC LMB

Project summary
The evolution of life likely required early systems to replicate both their genetic material and their compartments. We hypothesise that a primitive cell cycle could emerge if ribozymes were capable of both self-replication and membrane modification. Yet, no study has shown a direct functional link between ribozyme activity and membrane remodelling.
By exploring this previously uncharted intersection between primitive membranes and catalytic RNAs, the project will provide insight into one of the most fundamental transitions in the origin of life, by identifying and characterising lipid-modifying ribozymes, and studying their effect on membrane composition, properties and functions

Importance of the area of research concerned
How did early life evolve the capacity to replicate, divide, and evolve? While modern cells link genotype to phenotype through complex machinery, primitive cells may have established this connection through far simpler means via catalytic RNA (ribozymes) capable of modifying the lipid composition of primitive membranes. This project aims to uncover whether ribozymes can catalyse chemical modifications of primitive lipids and, in doing so, establish a direct genotype-phenotype coupling in primitive cell models. Overall, this project will pave the way towards the emergence of self-modifying primitive cells capable of undergoing growth and division.

What the student will actually do?
This project will develop directed evolution technologies for the identification of lipid-modifying ribozymes, drawing inspiration from known catalytic RNA motifs (e.g., phosphorylating ribozymes).
A generalised in vitro ribozyme selection approach will be implemented to isolate and enrich sequences that induce detectable changes in membrane composition or behaviour. Modulation of membrane features, such as curvature induction and phase separation, will be monitored using light microscopy, fluorescence and Raman spectroscopy. Ultimately, the most promising ribozymes will be tested in tandem with self-replicating ribozymes to investigate the compatibility between ribozyme-driven membrane modification and nucleic acid replication in a primitive cell model.

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.

References

Li Y., Horton N. G., O’Flaherty D. K., Rubio-Sanchez R.*, and Bonfio C.* – Beyond charge: hydrophobic features control selective DNA-membrane association. Submitted (2025).
Gianni E., Kwok S. L. Y., Wan C. J. K., Goeij K., Clifton B. E., Attwater J., Holliger P. – A polymerase ribozyme that can synthesize both itself and its complementary strand. bioRxiv (2024). doi: https://doi.org/10.1101/2024.10.11.617851.
Aleksandrova M., Rahmatova F., Russell D. A., Bonfio C.* – Ring-opening of glycerol cyclic phosphates leads to a diverse array of potentially prebiotic phospholipids. JACS (2023), 145, 25614-25620

PI: David Buscher, db106@cam.ac.uk, Department of Physics

Project summary
The project aims to further develop a recently-proposed method for wavelength calibration of spectrographs. The method involves injecting the output of a Michelson interferometer into the input to a high-resolution spectrograph. The resulting spectra show constructive and destructive interference at specific wavelengths which depend on the optical path difference in the interferometer. Analysis of these interference patterns is used to derive very high precision estimates of the relative wavelengths the pixels of the spectrograph.

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 the student will actually 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.

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, and an interest in computer control of hardware, and data analysis.

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.

Terrestrialization Tipping Points: A Statistical and Sedimentary Geological Analyses of Trace Fossil Record of the Devonian Critical Zone

PI: Neil Davis, nsd27@cam.ac.uk, Department of Earth Sciences
CO-I: Emily Mitchell, ek338@cam.ac.uk, Department of Zoology

Project summary
The Devonian is a key interval of terrestrialization and sedimentary rocks of this age are well represented in the region of NW Europe, rendering it a perfect natural laboratory to assess animal impacts in different environments. Three sites act as case studies (North Devon Basin, England; Orcadian Basin, Scotland; Hornelen Basin, Norway) where underexplored records of trace fossils (burrows, trackways, etc) occur in strata deposited in shallow marine, lacustrine, floodplain soil, and alluvial environments. Detailed documentation of the size, diversity and disparity of traces, anchored in a robust sedimentary geological framework and subjected to statistical analyses, will shed light on the Devonian critical zone and identify the role of pioneer animals as ecosystem engineers impacting geomorphology and weathering processes on scales from the local to global.

Importance of the area of research concerned
The critical zone is the region of the solid Earth where lithosphere meets biosphere and its operation involves a complex network of interactions between biological and geological processes, coupled on scales ranging from patches to global and from seconds to millennia. On land, this is most recognisable in the form of soils, where metazoans interact with other life (plants, fungi, etc) and parent rock, occupying deep horizons for stability, or surface horizons for a greater environmental variability, opportunities and challenges. We presently lack an informed understanding of how this critical zone developed at the onset of animal life on land, which was absent for the first 90% of Earth history. Such an understanding will impart new perspectives on the complex system that is today a key regulating venue for biodiversity, climate and the hydrosphere. Focussed analysis of key Devonian sites will isolate the timing of novel terrestrial behaviours, recognise how the critical zone expanded as animals occupied increasingly deeper tiers, and identify direct impacts on local physical geomorphology and lithological materials that can be extrapolated to have multiplied into global impacts.

What the student will actually do?
The student will undertake several field seasons at the three sites to map out trace fossil bedding planes and document the diversity, size and disparity of trace fossils in environments that provide a transect from marine to continental environments. Ichnofauna unique to different environments will be documented and statistical analysis of facies-crossing forms will be undertaken to assess marine vs. non-marine variability in spatial behaviour, size, density and depth of burrow systems. Original field data from the three sites will be augmented with a comparison of other global ichnofaunas, assembled as a database from pre-existing records. Sedimentary geological data will allow the depth of tiering of burrows to be recognised. Samples will be taken for thin section and SEM analysis of burrowed profiles to identify variability in clay mineral petrography associated with burrow formation and to recognise microscale impacts on lithology and the material properties of sediment piles.

Requirements as to the educational background of candidates that would be suitable for the project
This project requires a background in Earth Sciences and/or Palaeontology.

References

Buatois, L.A., Davies, N.S., Gibling, M.R., Krapovickas, V., Labandeira, C.C., MacNaughton, R.B., Mángano, M.G., Minter, N.J. and Shillito, A.P., 2022. The invasion of the land in deep time: integrating Paleozoic records of paleobiology, ichnology, sedimentology, and geomorphology. Integrative and Comparative Biology, 62(2), pp.297-331.
Genise, J.F., Bedatou, E., Bellosi, E.S., Sarzetti, L.C., Sánchez, M.V. and Krause, J.M., 2016. The Phanerozoic four revolutions and evolution of paleosol ichnofacies. The Trace-Fossil Record of Major Evolutionary Events: Volume 2: Mesozoic and Cenozoic, pp.301-370.
Van Straalen, N.M., 2021. Evolutionary terrestrialization scenarios for soil invertebrates. Pedobiologia, 87, p.150753.

PI: Alex Liu, agscl2@cam.ac.uk, Department of Earth Sciences
CO-I: Dave Lowe, dlowe@mun.ca, Memorial University of Newfoundland, Canada

Project summary
This project will document the stratigraphic occurrence and paleoenvironmental setting of individual taxa within the late Ediacaran Catalina Dome. Geological mapping and facies analysis will permit correlation of individual sections and interpretation of the palaeoenvironments inhabited by organisms. Combining these data with existing geochronological data, we will develop a time-calibrated stratigraphic range chart for taxa in the region, and compare this with other regional and global datasets to develop and test hypotheses regarding evolution and radiation. The project will constrain both the specific depositional settings in which complex animal life evolved, and the timing of evolutionary progress within these ecosystems.

Importance of the area of research concerned
Establishing the timing and trajectory of early animal evolution is vital to efforts to determine the processes responsible for generating Earth’s incredible diversity of animals, and the environmental conditions that nurtured the origination of complex life. Fossils of the Ediacaran macrobiota preserve Earth’s earliest record of large and complex multicellular life, and sites in Newfoundland (Canada) offer some of the oldest fossil assemblages of these organisms. Time-calibrated stratigraphic ranges for Ediacaran taxa in southeastern Newfoundland offer opportunities to develop hypotheses regarding evolutionary trajectories within the Ediacaran biota, but these hypotheses cannot be tested without independent records from other regional and global sites. This project will collect sedimentological and palaeontological data from the Catalina Dome on the Bonavista Peninsula of Newfoundland to document palaeoenvironmental proxies and stratigraphic ranges of taxa there, to ultimately permit distinction between the competing environmental, evolutionary and taphonomic controls on observed fossil distributions of early animals.

What the student will actually do?
You will conduct fieldwork in Newfoundland, Canada, to document petrological, sedimentological and palaeontological data across the Catalina Dome, and to map and correlate individual units and bedding planes in order to construct a coherent stratigraphic column for the region. By incorporating geochronological data from collaborators, you will develop an age model to calibrate your fossil occurrence data, and compare this to existing and novel datasets from elsewhere in Newfoundland, to develop and then test hypotheses regarding the major environmental, preservational or evolutionary controls on observed fossil occurrence. Opportunities are available for interested applicants to expand their research to consider nearby sections on adjacent peninsulas, conduct taxonomic work to describe new taxa, or to consider broader basin evolution. There may also be opportunities for successful students to spend an extended period of time at Memorial University to work closely with the co-supervisor on aspects of process sedimentology and paleoenvironmental analysis.

Requirements as to the educational background of candidates that would be suitable for the project
Earth Sciences undergraduate or Masters backgrounds preferred.

References

Matthews, J. J., Liu, A. G., Yang, C., McIlroy, D., Levell, B., & Condon, D. J. (2021). A chronostratigraphic framework for the rise of the Ediacaran macrobiota: new constraints from Mistaken Point Ecological Reserve, Newfoundland. GSA Bulletin, 133(3-4), 612-624.

This paper presents a time-calibrated fossil occurrence dataset for the Mistaken Point Ecological Reserve (Avalon Peninsula), which will form the main comparative dataset for the new data collected in this project.

Hofmann, H. J., O'Brien, S. J., & King, A. F. (2008). Ediacaran biota on Bonavista Peninsula, Newfoundland, Canada. Journal of Paleontology, 82(1), 1-36.

The original paper documenting Ediacaran fossils on the Bonavista Peninsula, which includes a preliminary range chart for individual taxa. Multiple discoveries of new surfaces and taxa by our research group since 2008 have doubled the number of known fossil-bearing surfaces.

Mason, S. J., Narbonne, G. M., Dalrymple, R. W., & O’Brien, S. J. (2013). Paleoenvironmental analysis of Ediacaran strata in the Catalina Dome, Bonavista Peninsula, Newfoundland. Canadian Journal of Earth Sciences, 50(2), 197-212.

The most recent description of the palaeoenvironments documented within the Catalina Dome stratigraphic succession. Recent work conducted by Co-S Lowe’s research group elsewhere on the Bonavista and Avalon peninsulas is refining our understanding of basin evolution in this region.

PI: Oliver Shorttle, os258@cam.ac.uk, Institute of Astronomy and Department of Earth Sciences
CO-I: David Hodell, Department of Earth Sciences, dah73@cam.ac.uk
Sasha Turchyn, Department of Earth Sciences, avt25@cam.ac.uk
Elizabeth Harper, Department of Earth Sciences, emh21@cam.ac.uk

Project 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 the student will actually 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.

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.

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.

PI: Paul B Rimmer, pbr27, Department of Physics – Cavendish Laboratory
CO-I: Sai Shruthi Murali, ssm54, Department of Physics – Cavendish Laboratory

Project 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.

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

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

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

PI: Helen Williams,hmw20@cam.ac.uk,Department of Earth Sciences
Alexandra Turchyn, avt25@cam.ac.uk, Department of Earth Sciences

Project summary
Studying submarine basalt weathering is challenging to study due to the prohibitive costs of acquiring samples; Iceland provides a natural environment that has the same chemical weathering reactions and exposure to saline solutions from the nearby ocean. Moreover, the cold temperatures under which weathering reactions take place on Iceland makes Iceland a suitable natural lab for considering surface processes on early Mars. This project will also focus on a unique natural hotspot: the Jas Roux site (France)This project seeks to further our knowledge about the processes of submarine basalt weathering through a field and laboratory incubation study using basalt from Iceland.

Importance of the area of research concerned
Over 4 billion years of Earth history, our climate and surface temperature have remained stable. This requires a self-driving thermostat regulating our climate via the geological carbon cycle. What allows the carbon cycle to act as such a thermostat over Earth history has long been thought to be terrestrial silicate weathering, but basalt weathering is particularly important. Basalt is a particular silicate rock whose chemical weathering is most directly temperature sensitive. It has become increasingly understood that basalt weathering across Earth’s surface environment is a key part of ANY silicate weathering feedback; although basalt covers only 5% of Earth’s continental surface, weathering of this basalt is thought to generate 30-40% of the alkalinity flux to the Earth’s oceans. Submarine basalt weathering, that is under the oceans, may be particularly important both in stabilising early Earth’s carbon cycle, and that of other terrestrial planets such as Mars. Basalt is highly abundant on the surface of Mars, as revealed by the Perseverance mission to the Jezero crater, and it has also highly likely that Mars once had liquid oceans. Submarine basalt weathering is therefore likely to have occurred on Mars, with considerable impacts on Martian surface chemistry and habitability.

What the student will actually do?
The student will sample rocks and rivers/streams in Iceland, characterising the salinity of the water and the major element composition of the streams, as well as the oxygen, sulfur, lithium and thallium isotope ratios. Oxygen allows us to characterise the water, sulfur tells us any sulfate reduction that is occurring, lithium reacts strongly into the rock during basalt weathering, as does thallium, which is particularly taken up into sulfide minerals. Rocks will be brought back to Cambridge, where they will be homogenised and put in incubation vessels to explore weathering reactions. The student will target both magnesium-rich basalts, which were likely abundant on the surface of the early Earth, and more iron-rich samples, which are a closer match to Martian samples. They will also have the opportunity to work on wehrlite samples that were recently identified as analogues for the Seitah formation present in the Jezero crater.

Requirements as to the educational background of candidates that would be suitable for the project
This project would be suited to a student with a background in Earth Sciences, Physical Geography or Chemistry.

References

Gaudin, A., Dehouck, E., & Mangold, N. (2011). Evidence for weathering on early Mars from a comparison with terrestrial weathering profiles. Icarus, 216(1), 257-268.
Ostrander, C. M., Nielsen, S. G., Gadol, H. J., Villarroel, L., Wankel, S. D., Horner, T. J., ... & Hansel, C. M. (2023). Thallium isotope cycling between waters, particles, and sediments across a redox gradient. Geochimica et Cosmochimica Acta, 348, 397-409.
Coogan, L. A., & Gillis, K. M. (2018). Low-temperature alteration of the seafloor: impacts on ocean chemistry. Annual Review of Earth and Planetary Sciences, 46(1), 21-45.

PI: Alex Archibald, ata27@cam.ac.uk, Yusuf Hamied Department of Chemistry
CO-I: Megan Brown, majb4@cam.ac.uk, Yusuf Hamied Department of Chemistry

Project summary
Mars is a key analogue in the search for life beyond Earth. An accurate understanding of the atmospheric composition (chemistry) and climate of Mars is therefore crucial. However, despite significant improvement in our knowledge of these processes huge gaps persist. Recent modelling work has identified critical inabilities in state-of-the-art models for simulating the abundance of key species, specifically: O2, H2, CO and O3. Failure to accurately model these species hampers our ability to simulate Mars’ atmospheric chemistry-climate system over Mars’ history and so leaves us unable to probe with confidence questions about the habitability of Mars. In this project we will develop uncertainty quantification techniques to pinpoint key processes that drive the divergence between models and observations of Mars’ chemistry and couple these with model calibration techniques to constrain these errors, enabling improved modelling tools.

Importance of the area of research concerned
Atmospheric composition is not only a prism to view planetary habitability through, but it sets the environment for life to emerge. Accurately predicting how atmospheric composition changes under the major changes that have occurred over the history of our solar system is crucial to understanding how suitable an atmosphere is for life. Numerical models simulate atmospheric composition as an emergent property of 100s-1000s of coupled reactions that we know to be important. But these reactions, the building blocks of atmospheric chemistry, are uncertain. Work on Earth’s present-day atmosphere has highlighted that the uncertainty that comes from these reactions can be quantified and through the application of observational constraints, the model processes can be calibrated to yield optimal model simulations. This uncertainty quantification-calibration pipeline is transforming the field of climate science on Earth and is ripe for application to other planets. This project will utilise the concepts and tools being developed in the group focusing on terrestrial problems and apply them for the first time to Mars focused problems.

What the student will actually do? 
The student will start by developing a database of key uncertainties related to the chemical processes occurring in Mars’ present-day atmosphere. This database will then be probed through a hierarchy of simulations that sample this epistemic uncertainty including Monte Carlo experiments with box and 1D models, moving towards Perturbed Parameter Ensembles (PPEs) with state of the art 3D models. Observations from the Trace Gas Orbiter (TGO; NOMAD and ACS) will provide constraints and calibration techniques such as Goal Oriented Bayesian Optimal Experimental Design will be applied to enable the development of improved models for simulating the Mars atmospheric chemistry-climate system.

Requirements as to the educational background of candidates that would be suitable for the project
This project would be particularly suitable for students with backgrounds in the Physical Natural Sciences (Physics or Chemistry), Computational Sciences or Statistics. 

References

Holthuijzen, M.F., Chakraborty, A., Krath, E. and Catanach, T., 2025. Surrogate-based Bayesian calibration methods for climate models: a comparison of traditional and non-traditional approaches. arXiv preprint arXiv:2508.13071.
Timothy H. Mcconnochie, Scott J. Vanbommel, Daniel Y. Lo, Elise Wright Knutsen, Franck Montmessin, et al.. Comparing the Unexplained Variability of Molecular Oxygen in the Martian Atmosphere to Water Vapor and Argon. 10th International Conference on Mars, Lunar and Planetary Institute, Jul 2024, Pasadena, United States. pp.3534. 
Brown, M.A.J., Patel, M.R., Lewis, S.R., Holmes, J.A., Lefèvre, F., Mason, J.P. and Crismani, M., 2024. The role and lifetime of dissociative heterogeneous processes in improving simulated ozone on Mars. Journal of Geophysical Research: Planets, 129(7), p.e2024JE008302.
Smith, M.D., Daerden, F., Neary, L., Khayat, A.S., Holmes, J.A., Patel, M.R., Villanueva, G., Liuzzi, G., Thomas, I.R., Ristic, B. and Bellucci, G., 2021. The climatology of carbon monoxide on Mars as observed by NOMAD nadir-geometry observations. Icarus, 362, p.114404.
Adams, D., Scheucher, M., Hu, R., Ehlmann, B.L., Thomas, T.B., Wordsworth, R., Scheller, E., Lillis, R., Smith, K., Rauer, H. and Yung, Y.L., 2025. Episodic warm climates on early Mars primed by crustal hydration. Nature Geoscience, 18(2), pp.133-139.

2024-2025

Lead Supervisor: Claudia Bonfio, Department of Biochemistry

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

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf

Lead Supervisor: Amy Bonsor, Institute of Astronomy
Co-supervisors: Craig Walton, Department of Earth Sciences/ETH Zurich; Laura Rogers, Institute of Astronomy

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.

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

Lead Supervisor: David Buscher, Department of Physics
Co-supervisor: Clark Baker, Department of Physics

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.

Precambrian mudrock from source-to-sink: an Earth analogue to identify pre-multicellular life habitable environments that have high biosignature preservation potential

Lead Supervisor: Neil S. Davies, Department of Earth Sciences
Co-supervisor: William J. McMahon, Department of Earth Sciences

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.

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).

Lead Supervisor: Oliver Shorttle, Department of Earth Sciences and Institute of Astronomy
Co-supervisors: David Hodell, Department of Earth Sciences, Sasha Turchyn, Department of Earth Sciences, Elizabeth Harper, Department of Earth 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.

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.

Lead Supervisor: Alex Thom, Chemistry
Co-supervisor: Alex Archibald, Chemistry

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.

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.

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.

Lead Supervisor: Paul B Rimmer, Department of Physics
Co-supervisor: Sai Shruthi Murali, Department of Physics

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?

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.

Lead Supervisor: Helen Williams, Department of Earth Sciences
Co-supervisors: Ross Findlay, Department of Earth Sciences; Mahesh Anand, Department of Physical Sciences, The Open University; Richard Greenwood, Department of Physical Sciences, The Open University; Mike Zolensky, ARES, NASA Johnson Space Centre

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:

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?
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?
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].

Lead Supervisor: Mark Wyatt, Institute of Astronomy
Co-supervisor: Oliver Shorttle, Department of Earth Sciences, Institute of Astronomy; Alex Archibald, Department of Chemistry

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.

Lead Supervisor: Andrew Jardine, Department of Physics

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.

Lead Supervisor: Nick Tosca, Department of Earth Sciences
Co-supervisor: Ziwei Liu, Department of Earth Sciences

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).

2023-2024

Lead Supervisor: Mark Wyatt, Institute of Astronomy
Co-supervisor: Oliver Shorttle, Department of Earth Sciences, Institute of Astronomy; Alex Archibald, Department of Chemistry

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

Lead Supervisor: Alex Thom, Chemistry
Co-supervisor: Alex Archibald, Chemistry

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.

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, Life11 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).

Lead Supervisor: Oliver Shorttle, Department of Earth Sciences and Institute of Astronomy
Co-supervisors: Dr Amy Bonsor, Institute of Astronomy; Dr Mihkel Kama, UCL ;Prof Olivier Namur, KU Leuven

Brief summary
The PhD project represents a multi-disciplinary effort to link constraints on planet formation from across disk dynamics, disk thermochemistry, and planetary chemistry to understand whether short-period plants can form with the ingredients needed for life. Models of disk processes constrained by the latest disk observations will be used to predict the composition of planetary building blocks for short-period planets (input from co-supervisors Bonsor, Kama). These models will be benchmarked against the chemistry of solar system analogue, Mercury (input from co-supervisor Namur). The redistribution of and availability to life of the sulfur, carbon, and phosphorous within the planet following its formation will be calculated using recent experimental constraints (supervisors Namur, Shorttle)

Importance of the area of research concerned
Short period exoplanets are the most commonly discovered and are the most amenable to follow up observations. They are therefore an important class of object in our search for life. However, the building blocks of these planets may have formed in regions of their protoplanetary disks with more extreme conditions than those of Earth’s building blocks: experiencing higher temperatures and higher local enrichments of dust. Together, these factors mean they may form with a very different inventory of sulfur, carbon, and phosphorus compared to Earth. The key question this project will address is therefore whether planets forming in such environments can retain carbon, sulfur and phosphorus and thereby achieve chemical habitability. This result will be important for guiding our search for worlds with potential for abiogenesis, habitability, and life sustaining surface geochemistry.

What will the student do?
The student will trace the fate of sulfur, carbon and phosphorus through disk environments, into planetary building blocks, and into and through the planets themselves. The project will begin by linking the dynamics of dust transport through disks to the likely chemical enrichment of inner disk regions. This constraint will be used to calculate the composition of planet forming material and therefore the likely inventory of sulfur, carbon and phosphorus in the planets. The second step is to then trace the redistribution of these elements within the planets once formed. Here, the student will draw upon state-of-the-art experimental results to trace the incorporation of these elements into planetary cores, mantles, crusts and atmospheres. Predictions at this point will be made for the atmospheric chemistry of short period planets, using atmospheric growth models to link atmospheres to planetary interiors.

References

Sebastiaan Krijt, Mihkel Kama, Melissa McClure, Johanna Teske, Edwin A. Bergin, Oliver Shorttle, Kevin J. Walsh, Sean N. Raymond. Chemical Habitability: Supply and Retention of Life’s Essential Elements During Planet Formation. PPVII (2023)
https://arxiv.org/abs/2203.10056
Mihkel Kama, Oliver Shorttle, Adam K. Jermyn, Colin P. Folsom, Kenji Furuya, Edwin A. Bergin, Catherine Walsh, Lindsay Keller. Abundant refractory sulfur in protoplanetary disks. Astrophysical Journal. (2019)
https://arxiv.org/abs/1908.05169
Ebel and Alexander. Equilibrium condensation from chondritic porous IDP enriched vapor: Implications for Mercury and enstatite chondrite origins. Planetary and Space Science. (2011)
https://doi.org/doi:10.1016/j.pss.2011.07.017

Requirements as to the educational background of candidates that would be suitable for the project
The successful candidate should have a background in Astrophysics or Earth and planetary sciences.

Lead Supervisor: Prof Tim Lewens, Department of History and Philosophy of Science
Co-supervisor: Prof Oliver Shorttle, Institute of Astronomy/Department of Earth Sciences

Brief summary
This PhD project will broaden the basis of interaction between philosophy and the study of life in the Universe by taking a practice-focused approach, which pays closer attention to the conceptual dimensions of live questions within astrobiology and the biological sciences more generally. An example project that connects well with the expertise and teams of Lewens and Shorttle concerns the relationship between astrobiology and controversial calls for an ‘Extended Evolutionary Synthesis’ (EES). In this approach (e.g. Laland et al 2014) natural selection need not be the only agent of adaptive change. Instead, EES foregrounds the importance of niche-construction in evolutionary change and stasis. This places emphasis on the planetary context as a driver of adaptive change, raising the prospect of essentially different factors influencing biological change across the galaxy. By revisiting this underlying account of evolution, a new and more universal set of approaches to what life is may come into view.

Importance of the area of research concerned
Much philosophical work on astrobiology has been focused on two interlinked themes. These are the questions of (i) how ‘life’ should be defined in the context of the search for living things elsewhere in the Universe, and (ii) whether our engagement with organisms that have all (so far at least) been restricted to just one planet biases our understanding of life in problematic ways. These very general topics are important, but they need to be supplemented by closer attention to conceptual problems that arise in the course of astrobiological practice (see Cirkovic 2012). Candidates will be invited to propose a specific formulation of a practice-oriented philosophical project that suits their interests and their training. The expectation of this project is that by expanding beyond astrobiology’s classic conceptual repertoire, it will be possible to formulate valuable new hypotheses for subsequent testing in the field of life in the Universe (Lewens 2020).

What will the student do?
As a philosophical project, it is essential that a significant element of the conception of the project comes from the student (guided by the project supervisors). The first year will consist of producing a refined vision for the research questions to be asked,. This will be generated via a literature survey of existing philosophical work on astrobiology, coupled to close engagement with astrobiological practice (achieved through regular sessions with Shorttle’s group). Applicants will be asked to articulate a potential approach at the moment of application. The student will be expected to participate in relevant LCLU reading groups and other events, and also to attend the regular weekly meetings of Lewens’s research group (which currently includes two other PhD students working on astrobiology). The student will be expected to complete two articles by the end of the tenure of the studentship, with one placed in a leading philosophy of science journal, the other (co-authored) in a relevant science journal.

References

Cirkovic, M. (2012) The Astrobiological Landscape. Cambridge: CUP.
Kevin Laland, Tobias Uller, Marc Feldman, Kim Sterelny, Gerd B. Müller, Armin Moczek, Eva Jablonka, John Odling-Smee, Gregory A. Wray, Hopi E. Hoekstra, Douglas J. Futuyma, Richard E. Lenski, Trudy F. C. Mackay, Dolph Schluter and Joan E. Strassmann (2014) ‘Does Evolutionary Theory Need a Rethink?’ Nature 514: 161-164.
Lewens, T. (2020) ‘How can conceptual analysis contribute to scientific practice? The case of cultural evolution.’ in T. Uller and K. Kampourakis (eds.) Philosophy of Science for Biologists. Cambridge: Cambridge University Press: pp. 146-167.

Requirements as to the educational background of candidates that would be suitable for the project
The successful candidate should have a Masters-level qualification with distinction in philosophy of science, ideally with sub-specialisation in philosophy of biology. Some level of background training in areas of basic science linked to the study of life in the Universe would also be valuable. The overall area of research for the student is specified broadly in this proposal, and the more detailed EES project suggested above is merely indicative. Prospective candidates should submit their own specific proposal for practice-based work on the philosophical foundations of astrobiology, which will be assessed by the supervisors.

Lead Supervisor: Richard Harrison, Department of Earth Sciences
Co-supervisor: Nick Tosca, Department of Earth Sciences

Brief summary
PIXL datasets, which include multispectral micro-context images and fluorescence data (which include diffraction phenomena), will be analysed using a new automated machine-learning approach – SIGMA (Tung et al., 2023). SIGMA, a machine-learning workflow successfully applied to analyses of Energy-dispersive X-ray spectroscopy (EDS) data, is particularly suited to study the mixed signals on XRF data from Mars and should provide sizeable improvement to how things are currently done. The analysis will also include comparing results to existing methods and assessing errors and artefacts.

Importance of the area of research concerned
This is a cross-disciplinary project that aims to apply novel computational analyses to X-ray fluorescence (XRF) datasets recently acquired by the Mars 2020 Perseverance Rover at Jezero Crater. The Planetary Instrument for X-ray Lithochemistry (PIXL) has returned micro-focused XRF data of igneous and sedimentary rocks approximately 3.5-3.8 billion years old (Farley et al., 2022; Tice et al., 2022), and these data are being used to inform short- and long-term exploration strategies of Jezero Crater and the selection of drill core samples to be acquired and eventually returned to Earth. However, like other energy-dispersive spectroscopic datasets, PIXL data suffer from a problem of non-uniqueness; it is often difficult, if not impossible, to confidently determine which minerals may be present in a given analysis. The project will result in a family of solutions for the mineral species present in ancient rocks on Mars, as well as their textural relationships. This raises the possibility that the project can directly contribute to the major scientific goals of the Mars 2020 mission, which is to characterize ancient habitable environments on the surface of Mars, and select samples most likely to record evidence for ancient life, if present.

What will the student do?
Identification of unknown micro- and nano-sized mineral phases is commonly achieved by analyzing chemical maps generated from hyperspectral imaging data sets, particularly scanning electron microscope—energy dispersive X-ray spectroscopy (SEM-EDS). However, the accuracy and reliability of mineral identification are often limited by subjective human interpretation, non-ideal sample preparation, and the presence of mixed chemical signals generated within the electron-beam interaction volume. Machine learning has emerged as a powerful tool to overcome these problems. The student will apply a machine-learning approach to data being collected on Mars using the PIXL instrument, with the aim of performing automated quantitative analyses of the mineralogy within Jezero crater. The student will compare results to existing methods and assess errors and artefacts. The student will write a Python code to adapt SIGMA to load and process the XRF data sets. They will then use three different approaches: conventional methods, multivariate statistical analysis, and then the latest neural-network-based SIGMA workflow to provide a quantitative breakdown of the mineralogy. Benchmarking and comparison among these three approaches will also be performed. The student will then consider what the results of this analysis mean in terms of the core science questions of the mission.

References

Farley, K. A. et al. Aqueously altered igneous rocks on the floor of Jezero crater, Mars. Science, 377, 6614, 2022.
Tice M. M., Hurowitz J. A., Allwood A. C., Jones M. W. M., Orenstein B. J., Davidoff S., Wright A. P., Pedersen D. A. K., Henneke J., Tosca N. J., Moore K. R., Clark B. C., McLennan S. M., Flannery D. T., Steele A., Brown A. J., Zorzano M.-P., Hickman-Lewis K., Liu Y., VanBommel S. J., Schmidt M. E., Kizovski T. V., Treiman A. H., O’Neil L., Fairén A. G., Shuster D. L., Gupta S. and Team T. P. (2022) Alteration history of Séítah formation rocks inferred by PIXL x-ray fluorescence, X-ray diffraction, and multispectral imaging on Mars. Science Advances 8, eabp9084, 2022.
Tung, P.-Y., Sheikh, H. A., Ball, M., Nabiei, F., & Harrison, R. J. (2023). SIGMA: Spectral interpretation using Gaussian mixtures and autoencoder. Geochemistry, Geophysics, Geosystems, 24, e2022GC010530. https://doi. org/10.1029/2022GC010530

Requirements as to the educational background of candidates that would be suitable for the project
Any background in the natural sciences will be suitable.

Precambrian mudrock from source-to-sink: an Earth analogue to identify pre-multicellular life habitable environments that have high biosignature preservation potential

Lead Supervisor: Neil S. Davies, Department of Earth Sciences
Co-supervisor: William J. McMahon, Department of Earth Sciences

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.

Lead Supervisor: David Buscher, Department of Physics

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf

Lead Supervisor: Amy Bonsor, Institute of Astronomy
Co-supervisors: Craig Walton, Department of Earth Sciences/ETH Zurich; Laura Rogers, Institute of Astronomy

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

Lead Supervisor: Claudia Bonfio, Department of Biochemistry

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.

Lead supervisor: Didier Queloz, Cavendish Astrophysics
Co-supervisor: Clark Baker, Cavendish Astrophysics

Brief summary
The measurement of the radial-velocity signal of an Earth-twin is by no means easy. The semi-amplitude of the radial-velocity signal induced by Earth orbiting around our Sun is ~9cm/s (~speed of a baby crawling). This signal is then buried in noise from the stellar-activity of the star; on the order of several m/s. As such, it is of utmost importance to have a stable and precise instrument (HARPS3) that is accurately characterised.

The student’s goal is, as a part of a team, understand the instrument and measurement processes sufficiently that the instrument can be characterised at the ~cm/s level.

Importance of the area of research concerned
An Earth-twin exoplanet is yet to be discovered and is of great scientific interest. A catalogue of discovered Earth-twins will not only allow us to better understand our own planet (and place in the universe) but also provide a major stepping stone in the search for life in the Universe.

The cutting edge, third generation of the highly successful High-Accuracy Radial-velocity Planet Searcher: HARPS3 is currently being assembled at Cambridge and will be commissioned on the Isaac Newton Telescope in La Palma in late 2024.

HARPS3 will engage in a, world-leading, intensive study for Earth-like planets orbiting around Sun-like stars, measuring the radial-velocity of ~30 Sun-like stars ‘nightly’ over the period of a decade in order to be sensitive to the signal of an Earth-like planet orbiting around these stars.

What will the student do?
HARPS3 will be assembled and commissioned in La Palma at the end of 2024, coinciding with the start of the student’s PhD. This will provide the student an unrivalled opportunity to learn about highly-stabilised, high-resolution spectrographs by being involved in the commissioning team of HARPS3.

During the commissioning, the student will contribute to the assembly of HARPS3, followed by verification activities; where the instrument and its subsystems are tested to ensure they are performing correctly.

With the instrument assembled and operating, the student will engage in a project to characterise the radial-velocity measurement and instrument-performances of HARPS3, including looking at correlation between a suite of environmental-sensors and the measurements of HARPS3. A key step in ensuring our instrument is ready to search for Earth-twins.

With the understanding gained by these works, the student will look to apply for time on HARPS3 to engage in the radial-velocity follow-up of transiting exoplanets.

References
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
Clark, Didier and the rest of the HARPS3 team will teach the student the basics of radial-velocity measurement, exoplanet study and highly-stabilised, high-resolution spectrographs during the commissioning of HARPS3 at the Isaac Newton Telescope (learning in a practical environment). Following this, the student will be supervised by Clark and Didier during the data-analysis sections of the project.

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2025-2026

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf

Terrestrialization Tipping Points: A Statistical and Sedimentary Geological Analyses of Trace Fossil Record of the Devonian Critical Zone

2024-2025

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf

Precambrian mudrock from source-to-sink: an Earth analogue to identify pre-multicellular life habitable environments that have high biosignature preservation potential

2023-2024

Precambrian mudrock from source-to-sink: an Earth analogue to identify pre-multicellular life habitable environments that have high biosignature preservation potential

Searching for signs of geological and biological evolution in exoplanetary systems using white dwarf