Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry

Abstract

A key challenge in origin-of-life studies is understanding the environmental conditions on early Earth under which abiogenesis occurred. While some constraints do exist (e.g., zircon evidence for surface liquid water), relatively few constraints exist on the abundances of trace chemical species, which are relevant to assessing the plausibility and guiding the development of postulated prebiotic chemical pathways which depend on these species. In this work, we combine literature photochemistry models with simple equilibrium chemistry calculations to place constraints on the plausible range of concentrations of sulfidic anions (HS${}^{-}$, HSO${}_3^{-}$, SO${}_3^{2-}$) available in surficial aquatic reservoirs on early Earth due to outgassing of SO${}_2$ and H${}_2$S and their dissolution into small shallow surface water reservoirs like lakes. We find that this mechanism could have supplied prebiotically relevant levels of SO${}_2$-derived anions, but not H${}_2$S-derived anions. Radiative transfer modelling suggests UV light would have remained abundant on the planet surface for all but the largest volcanic explosions. We apply our results to the case study of the proposed prebiotic reaction network of Patel et al. (2015), and discuss the implications for improving its prebiotic plausibility. In general, epochs of moderately high volcanism could have been especially conducive to cyanosulfidic prebiotic chemistry. Our work can be similarly applied to assess and improve the prebiotic plausibility of other postulated surficial prebiotic chemistries that are sensitive to sulfidic anions, and our methods adapted to study other atmospherically-derived trace species.

Accepted to Astrobiology; comments welcome

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Cited by in corpus (7)

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• Nitrogen Oxide Concentrations in Natural Waters on Early Earth
• UV Transmission in Natural Waters on Prebiotic Earth
• Sulfate Aerosol Hazes and SO2 Gas as Constraints on Rocky Exoplanets' Surface Liquid Water
• Cosmic dust fertilization of glacial prebiotic chemistry on early Earth
• H${}_2$-dominated Atmosphere as an Indicator of Second-generation Rocky White Dwarf Exoplanets
• Molecules with ALMA at Planet-forming Scales (MAPS) XII: Inferring the C/O and S/H ratios in Protoplanetary Disks with Sulfur Molecules