Sprecher
Beschreibung
Paul Rimmer
Prebiotic chemistry often begins with a desired product such as a nucleotide, an amino acid, a metabolic intermediate, and then seeks its production from geochemically plausible starting conditions. However, there is a range of plausible conditions for aqueous chemistry on early Earth, with a variety of pH's and temperatures, as well as light, various salts, and minerals. With such variety, it can be a challenge to constrain how much of a molecule is available for prebiotic experiments, let alone how a group of molecules would actually behave in a natural environment. Product-driven chemistry shows us what is possible; kinetics is needed to inform where this chemistry is possible, how long it lasts, and what else happens at the same time.
Cyanide is a useful seed molecule for prebiotic chemistry, but it degrades in water. Its survival in water allows us to determine an upper limit on its lifetime. I will show measured cyanide hydrolysis rates in pure water and water with a range of salts over 60–100°C and pH 4–12, and used a Bayesian Arrhenius analysis to extrapolate cyanide lifetimes down to 0°C across a wide range of plausible aqueous environments. These rates connect atmospheric or hydrothermal cyanide production to the maximum cyanide available in lakes, rivers, and ponds, as well as a range of formamide concentrations, suggesting where, if anywhere, formamide-rich solvents might arise naturally.
I will then show how this chemistry can be modelled using SOUP, an aqueous prebiotic chemical kinetics model. I will show how this model helps inform new work on ferrocyanide reformation from its photoaquated product. With these experiments and models, we aim to learn what chemical system each environment can produce. Some environments may have the right seeds for prebiotic chemistry, along with the right range of conditions for those seeds to grow into something that more closely resembles a living system. It may well be that most seeds fail to thrive in most environments. Failed harvests may leave behind the clearest signatures of their chemical causes.