Paul Rimmer, Ph.D.

Education:The Ohio State University, Ph.D., Physics
Institution: University of Cambridge

SCOL Project: Laboratory Simulations for Prebiotic Chemistry on the Surface of Early Earth and Other Planets

Recent laboratory investigations into prebiotic chemistry indicate that the building blocks of life likely originated from ultraviolet chemistry involving hydrogen cyanide, cyanamide, cyanoacetylene, phosphates and bisulfite in a pool or stream of water on the surface of early Earth. It is important to investigate this chemistry within a realistic geological context. In what sort of environment could all of these molecules be present together, either stored in appreciable quantities or being continuously replenished? Once candidate environments are identified, which environments best support the subsequent prebiotic chemistry?

These environments need not be relegated to those that may have plausibly been present on early Earth, a time for which there is scant information from the geological record. Other planets in and outside our solar system provide candidate environments within which we can investigate this prebiotic chemistry. My project investigating a wide range of local environments plausible on exoplanet surfaces will help address two distinct questions: (1) On what planets is an origin of life most likely? (2) What does prebiotic chemistry say about geochemistry? Exploring exotic environments, I hope to identify some common features for those environments in which the prebiotic chemistry works best. These common features can then be applied to early Earth, indicating what sort of environments would likely have been present more than 3.5 billion years ago, without which life on Earth would have been unlikely.

I go about this by first modeling the magma, surface and atmospheric chemistry for exoplanets over a wide range of compositions, considering photochemistry, lightning, impacts, volcanic outgassing and ongoing surface processes. I combine these models with experiments performed with colleagues at Cambridge Earth Sciences and the Czech Academy of Sciences, where the above conditions can be reproduced in the lab. The eventual output of these models and experiments can be used to inform what starting chemistries are plausible for the prebiotic synthesis of life’s building blocks on the surface of a rocky exoplanet. I will then work with colleagues at the Laboratory of Molecular Biology to investigate these starting chemistries using a simulator that reproduces the light of that planet’s star, including the stellar flares. This simulator will be designed in collaboration with colleagues at Cavendish Astrophysics, in order to ensure that the ultraviolet spectrum used in the lab faithfully represents the UV light of the star in question.

I will use the results of these experiments, along with the stellar and planetary properties of known potentially habitable exoplanets, in order to rank which planets make the best candidates in the search for life. At the same time, I will look into how the results of these experiments may reveal under what conditions life likely originated on early Earth, allowing prebiotic chemistry to inform the geochemistry.