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Alternative Earths and their habitability for complex life


Key facts

Type of research degree
Application deadline
Friday 31 May 2024
Project start date
Tuesday 1 October 2024
Country eligibility
UK only
Source of funding
Research council
Dr Benjamin Mills
Additional supervisors
Alexander Krause (Leeds), Andrew Rushby (UCL/Birkbeck), Christopher Colose (NASA GISS)
School of Earth and Environment
<h2 class="heading hide-accessible">Summary</h2>

This fully funded PhD place provides an exciting opportunity to pursue postgraduate research in Earth science and astrobiology.<br /> <br /> The list of &lsquo;potentially Earth-like&rsquo; rocky exoplanets in the galaxy continues to grow, and recent instrumental advances are paving the way to the analysis of their atmospheric compositions. But which planets should we study in more detail? Are planets larger or smaller than Earth more likely to host complex (e.g. multicellular or eukaryotic) life? Should we be looking around stars larger or smaller than our own Sun? Do planets need to be of a certain age before complex life becomes possible? The answers to these questions hinge on a better understanding of how our own planet has changed over time, which can be achieved by building a quantitative computer simulation of the broad aspects of the evolution of the planetary surface environment, and comparing its predictions to the known changes on Earth. With such a &lsquo;Planetary System Model&rsquo;, rather than the more typical &lsquo;Earth System Model&rsquo;, we can replay the tape of environmental and biotic evolution on Earth, and then re-run this experiment for simulated planets which may be very different to our own. <br />

<h2 class="heading hide-accessible">Full description</h2>

<p>In this project, the student will build on world-leading research into long-term Earth surface evolution, expanding our current computer models for the long-term development of the key tectonic, biotic and chemical cycles (e.g. Alcott et al. 2019; Krause et al., 2022; Rushby et al., 2018) to include a broader suite of metabolisms and processes (e.g. Zhao et al., 2023) that will allow us to simulate the overall habitability of a planet for Earth-like complex life (e.g. high O2, low H2S, tolerable temperatures, pH, salinity). It will be possible to write this new model from scratch in whatever programming language the student prefers, or to begin from one of our already-published models written in python or MATLAB (e.g. see ). No specific background knowledge is required and we aim to provide bespoke training in the required skills. We will first test the model framework by comparing its reconstruction of Earth&rsquo;s surface conditions to multiple lines of geological and geochemical evidence, and we expect to publish high quality work (e.g. in the same high impact journals as our work above) both on the evolution of the Earth and on the application of the model to hypothetical and real exoplanet environments.</p> <p><strong>Working environment</strong><br /> The research will be based in Mills&rsquo; Earth Evolution Modelling Group, which is part of the Earth Surface Science Institute (ESSI), within the School of Earth and Environment at the University of Leeds. ESSI is a medium sized and friendly research institute that includes analytical geochemists, biogeochemists, sedimentologists, palaeontologists and modellers of climate and biogeochemistry. The group holds several annual science and social events and weekly informal get-togethers. Project supervisor Mills has received multiple ESSI &lsquo;Star Supervisor&rsquo; awards. For more information on the research group see <a href=""></a>.&nbsp;</p> <p><strong>Entry requirements</strong><br /> This project would suit somebody with a degree in one of the natural sciences, mathematics or computing, and the candidate should have a strong interest in Earth history and planetary surface environments. Formal training in numerical techniques is not essential, but enthusiasm for computing is advisable. All necessary training will be provided as part of the project.</p> <p><strong>Information about the Award</strong><br /> We are offering 1 full-time PHD scholarship in the School of Earth and Environment for one UK candidate, matching UKRI maintenance stipend and UK tuition fees for three and a half years, subject to satisfactory progress.&nbsp;</p> <p><strong>Duration of the Award</strong><br /> Full-time (3.5 years). The award will be made for one year in the first instance and renewable for a further period of up to two and a half years, subject to satisfactory academic progress.</p> <p><strong>Other Conditions</strong></p> <ul> <li>Applicants must not have already been awarded or be currently studying for a doctoral degree.</li> <li>Awards must be taken up by 1st October 2025.</li> <li>Applicants must live within a reasonable distance of the University of Leeds whilst in receipt of this scholarship.<br /> &nbsp;</li> </ul> <p><strong>References</strong></p> <p>Alcott, L. J., Mills, B. J. W. &amp; Poulton, S. W. Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling. Science 366, 1333-1337 (2019).&nbsp;</p> <p>Krause, A., Mills, B., Merdith, A., Lenton, T. &amp; Poulton, S. Extreme variability in atmospheric oxygen levels in the late Precambrian. Science Advances 8, eabm8191 (2022).&nbsp;</p> <p>Rushby, A. J., Johnson, M., Mills, B. J. W., Watson, A. J. &amp; Claire, M. W. Long-Term Planetary Habitability and the Carbonate-Silicate Cycle. Astrobiology 18, 469-480 (2018).</p> <p>Zhao, M., Mills, B. J. W., Homoky, W. B. &amp; Peacock, C. L. Oxygenation of the Earth aided by mineral&ndash;organic carbon preservation. Nature Geoscience (2023).</p>

<h2 class="heading">How to apply</h2>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="">University&#39;s website</a>. Please state clearly in the research information section&nbsp;that the research degree you wish to be considered for is &ldquo;Alternative Earths and their habitability for complex life&rdquo; as well as&nbsp;<a href="">Prof Benjamin Mills</a> as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p>

<h2 class="heading heading--sm">Entry requirements</h2>

Applicants to this scholarship in the School of Earth and Environment should normally have a First class or 2:1 Undergraduate degree (or international equivalent) AND/ OR a Distinction or Merit (or predicted Distinction or Merit) in their Masters degree (both in an appropriate discipline). Applicants who are uncertain about the requirements for a particular research degree are advised to contact the Postgraduate Research Admissions Team prior to making an application.

<h2 class="heading heading--sm">English language requirements</h2>

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<h2 class="heading">Funding on offer</h2>

<p>One full scholarship is available in the School of Earth and Environment from October 2024. This scholarship is open to UK applicants and covers fees plus UKRI maintenance stipend (currently &pound;19,237 in 2024/25).</p>

<h2 class="heading">Contact details</h2>

<p>Professor Mills can be reached at for any questions about this project. See for more information about the Earth Evolution Modelling Group.</p> <p>If you have any questions regarding the application process, please contact the Postgraduate Research Admissions team for the Faculty of Environment:;</p>

<h3 class="heading heading--sm">Linked research areas</h3>