Water is crucial to life and its development, and may have been present on the Earth, possibly in the form of a global ocean, within its first few million years. Whilst some geochemical evidence exists for the presence of water early in Earth’s history, its chemical composition remains unclear. Understanding the chemical composition of the early ocean is important to help us understand what environmental conditions were needed for life to arise and thrive.
Regardless of the source of Earth’s water, the interaction between the early ocean and early crust would influence the composition of Earth’s ocean. Water-rock interactions at the ocean floor would have liberated elements necessary for life (CHNOPS), as well as those required for the generation of chemical energy (via reduction-oxidation reactions). Resulting in the three key requirements for life present in Earth’s early oceans.
The delivery of exogenous material, via impacts, may have also influenced the habitability of the Earth’s early ocean. The addition of cometary ices, particularly CO2, or the instantaneous chemical changes experienced by minerals and organic compounds could have contributed to changes in the Earth’s ocean composition, influencing its habitability.
This project aims to explore the composition of the Earth’s early ocean and understand the effect exogenous material would have had on its evolving habitability. It will use computer modelling and laboratory experiments to constrain the contributions made by water-rock interactions and meteorite impacts to the Earth’s ocean, and determine their influence on the energy available from redox reactions to support microbial life.
Figure 1: Artist’s impression of the early Earth’s ocean (Source: Mark Garlick/Science Photo Library/Alamy Stock Photo).
This project is not suitable for CASE funding
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The project begins by using existing literature to define a composition of the Earth’s early crust and primitive ocean. Using these compositions, computer modelling will be used to identify ocean composition and mineral reaction pathways for the early Earth. Further modelling will be conducted to examine the influence cometary ices would have on this early ocean composition. The Gibbs energy of redox reactions will be calculated to identify metabolic pathways that could be supported and the amount of energy available to microbial life.
Impact experiments will be conducted using the all-axis light gas gun at the Open University. Chondrite meteorite projectiles will be impacted into the modelled ocean composition at a range of velocities. The post-impact fluid and any surviving projectile material will be analysed using standard geochemical techniques to assess impact-induced changes to fluid composition and mineralogy. Further Gibbs energy calculations will be undertaken for the simulated system.
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
The student will be taught to use a range of computer modelling programs. They will also be trained to use the all-axis light gas gun, as well as geochemical analytical techniques (SEM, Raman and ICP-OES). As a part of this project, the student will also foster skills in communication, time management, data handling, and management of large datasets.
Dr Eva Stueeken is a Reader in the School of Earth and Environmental Sciences at the University of St Andrews. She has expertise in geochemistry and stable isotopes. Her research focuses on understanding the origin and evolution of life in environments on Earth, and its implications for the development of life on other planets.
Dr Richard Greenwood is a Senior Research Fellow within the School of Physical Sciences (Open University) and an expert in oxygen isotope analysis. His research aims to understand the early stages of the Solar System’s history.
Year 1 – Perform a literature review. Identify possible compositions for the Earth’s early crust and sources for terrestrial volatiles. Using the computer code CHIM-XPT model, water-rock interactions to determine a composition for the early Earth’s ocean. Present results at a national conference. Design impact experiments and preliminary tests using volatile-bearing minerals.
Year 2 – Complete preliminary tests and conduct impact experiments using samples of meteorite and model outputs. Analyse the fluid and the surviving projectile post-impact. Run Gibbs energy calculations on fluids. Present results at an international conference.
Year 3 – Conduct fluid mixing models to assess the effect cometary impacts would have on the ocean composition. Run Gibbs energy calculations. Present results at a national/international conference. Write and submit thesis.
Daly, R. Terik, and Peter H. Schultz. (2018) The Delivery of Water by Impacts from Planetary Accretion to Present, Science Advances, 4, 1–11. doi: 10.1126/sciadv.aar2632.
Greenwood, Richard C., Ian A. Franchi, Ross Findlay, James A. Malley, Motoo Ito, Akira Yamaguchi, Makoto Kimura, Naotaka Tomioka, Masayuki Uesugi, Naoya Imae, Naoki Shirai, Takuji Ohigashi, Ming Chang Liu, Kaitlyn A. McCain, Nozomi Matsuda, Kevin D. McKeegan, Kentaro Uesugi, Aiko Nakato, Kasumi Yogata, Hayato Yuzawa, Yu Kodama, Akira Tsuchiyama, Masahiro Yasutake, Kaori Hirahara, Akihisa Tekeuchi, Shun Sekimoto, Ikuya Sakurai, Ikuo Okada, Yuzuru Karouji, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Masahiro Nishimura, Toru Yada, Masanao Abe, Tomohiro Usui, Sei ichiro Watanabe, and Yuichi Tsuda (2023) Oxygen Isotope Evidence from Ryugu Samples for Early Water Delivery to Earth by CI Chondrites, Nature Astronomy, 7, 29–38. doi: 10.1038/s41550-022-01824-7.
Martins, Zita, and Matthew A. Pasek (2024) Delivery of Organic Matter to the Early Earth, Elements, 20, 19–23. doi: 10.2138/gselements.20.1.19.
Sekine, Toshimori, Chuanmin Meng, Wenjun Zhu, and Hongliang He. (2012) Direct Evidence for Decomposition of Antigorite under Shock Loadin, Journal of Geophysical Research: Solid Earth, 117,1–8. doi: 10.1029/2011JB008439.
Tyburczy, James A., Benjamin Frisch, and Thomas J. Ahrens. (1986) Shock-Induced Volatile Loss from a Carbonaceous Chondrite: Implications for Planetary Accretion, Earth and Planetary Science Letters, 80, 201–7. doi: 10.1016/0012-821X(86)90104-4.
Please contact Nisha Ramkissoon ([email protected]) for further information and an informal discussion about this project.
To apply to this project:
Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026.