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Dr Paul Brandon Rimmer

Dr Paul Brandon Rimmer

Simons Senior Fellow

Prebiotic Chemistry on Exoplanets

Atmospheric Chemistry

Astrochemistry

N293
Office Phone: +44 (0) 1223 333462

Biography:

I am a postdoc in the Department of Earth Sciences with affiliations at Cavendish Astrophysics and the MRC Labratory of Molecular Biology. I explore the diverse geochemical and astronomical contexts for prebiotic chemistry. My expertise is in chemical kinetics, primarily in the context of atmospheric chemistry and astrochemistry.

PhD in Physics from Ohio State University (2012) Advisers: Eric Herbst & Richard Freeman

BS in Physics from University of Colorado Health Sciences (2005)

Research Interests

I'm primarily exploring prebiotic chemistry proceeding from hydrogen cyanide and other feedstock molecules at high concentrations in surface environments. The two scenarios I explore in depth are impact-generated craters where cyanide and other feedstock molecules are stored in organometallic complexes, to be liberated by interaction with water and ultraviolet light, and then activated and transformed by that ultraviolet light. I explore these scenarios using a combination of theory and experiment.

Theory

I employ atmospheric and magma chemistry models based on a comprehensive chemical network that is valid for H/C/N/O chemistry, incorporating some metallic chemistry as well as limited (but growing) Cl/S/P networks. The models are benchmarked against observations of Earth, Mars, Jupiter, exoplanets (from ultra-hot to warm Jupiters), and, recently, Venus. These models are applied to atmospheres of varying oxidation states, representing the broad uncertainty about Earth's atmosphere during the Hadean (< 3.8 Ga), the time when life likely originated on Earth. They are used to model photochemistry, energetic particle chemistry, and chemistry induced by lightning and impacts. I work closely with colleagues who employ more robust and self-consistent magma chemistry, atmospheric evolution, energetic particle propagation and early impact models in the attempt to obtain a comprehensive view of the global atmospheric and surface environment of the Hadean Earth, and to provide insight about local environments within which the first chemical steps toward life may have occurred.

Experiment

I have designed an experimental apparatus to simulate plausible surface environments, by using lamps and filters to supply ultraviolet light that is similar to the young sun, and surfaces and mixtures supplied either by impacts or by magmatic outgassing. This apparatus is called StarLab, and resides at the MRC Laboratory of Molecular Biology. I also work on magma chemistry experiments to simulate ultra-reduced nitrogen-rich magmas, to find out if they can supply key feedstock molecules required for prebiotic chemistry, especially cyanoacetylene. The magma experiments will take place in Earth Sciences. I also collaborate closely with a research group in Prague lead by Martin Ferus, who simulate impacts. The results of their experiments and of my magma experiments inform what chemistries may have been present in these surface environments, and therefore what chemistry to start with in the StarLab.

Keywords

Geochemistry ; Computer Simulations

Topics

  • Magma mixing and ascent
  • Volcanology
  • Volatile geochemical cycling
  • Numerical Modelling

Key Publications

Rimmer, P.B. and Helling, C., 2016. A chemical kinetics network for lightning and life in planetary atmospheres. The Astrophysical Journal Supplement Series224(1), p.9.

Rimmer, P.B., Xu, J., Thompson, S.J., Gillen, E., Sutherland, J.D. and Queloz, D., 2018. The origin of RNA precursors on exoplanets. Science advances4(8), p.eaar3302.

Rimmer, P.B. and Shorttle, O., 2019. Origin of Life’s Building Blocks in Carbon-and Nitrogen-Rich Surface Hydrothermal Vents. Life, 9(1), p.12.

Rimmer, P.B., Ferus, M., Waldmann, I., et al. Identifiable Acetylene Features Predicted for Young Earth-like Exoplanets with Reducing Atmospheres undergoing Late Heavy Bombardment. Submitted to the Astrophysical Journal.