Do-Nothing Prebiotic Chemistry: Chemical Kinetics as a Window into Prebiotic Plausibility.

Abstract

ConspectusOrigin of Life research is a fast growing field of study with each year bringing new breakthroughs. Recent discoveries include novel syntheses of life's building blocks, mechanisms of activation and interaction between molecules, and newly identified environments that provide promising conditions for these syntheses and mechanisms. Even with these new findings, firmly grounded in rigorous laboratory experiments, researchers often find themselves uncertain about how to apply them. How can a bridge be built between the laboratory and the geochemical environment? A critical question to ask when seeking to apply new results in origins is: how can this chemistry occur without direct intervention from a chemist? We believe the first step toward answering this question lies in the determination of rate constants and the construction of chemical networks to describe prebiotic chemistry in geochemical environments.So far, our group has measured several rate constants relevant to different prebiotic reaction networks, starting with the synthetic pathways of the cyanosulfidic network. The reactions we explore often involve ultraviolet light-driven photochemistry, facilitated by our StarLab setup that accurately simulates the spectrum of the young Sun and other stars. Our latest work investigates environments with active photochemistry in the absence of cyanide. In this study, we measure the effective rate constant for the production of formate from the reduction of carbon species using sulfite within the context of early Martian waters. The underlying goal of the work done in our group is to predict the likelihood that certain geological conditions will result in a specific set of chemical products. These predictions can be combined with those we have made for the necessary astrophysical conditions in certain origins of life scenarios on extrasolar planets.In the near future we expect that a sufficient number of rate constants will be measured, by our group and others, to allow for aspects of prebiotic chemistry to be predicted using chemical kinetics models. Once these models have been benchmarked against experimental data, our next step will be applying them to natural environments that better mimic the conditions thought to have been present at the onset of life. Following this, we can test these models by comparing their predictions to additional experiments. After refinement, these models will be able to provide guidance on the optimal conditions for conducting laboratory experiments, while helping to minimize and characterize any interference from a chemist.This approach can provide valuable insights into what is possible within geochemical environments, where all chemistry is by necessity do-nothing chemistry.