Constraining a Cometary Source of Life’s Building Blocks
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?
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 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.
Applying
You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.