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.
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.
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
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.