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Will short-period planets contain life-essential elements?
Lead Supervisor: Oliver Shorttle, Department of Earth Sciences and Institute of Astronomy
Co-supervisor: 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. 

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)

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)

Ebel and Alexander. Equilibrium condensation from chondritic porous IDP enriched vapor: Implications for Mercury and enstatite chondrite origins. Planetary and Space Science. (2011)

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.

You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.