New Constraints on Sulfur Cycling in the Prebiotic Earth – GWC Mag

Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: AGU Advances

The abundance and chemical speciation of sulfur in the prebiotic Earth has implications for the chemical origins of molecular building blocks of life and the formation of UV-attenuating atmospheric hazes. For an atmosphere without free O₂, the abundance of sulfur in the +4-oxidation state (‘sulfite’), including the species SO₃^2-, HSO₃^– and SO₂, have been highly uncertain.

Using new experiments to quantify the rates of disproportionation and photolysis of aqueous sulfite coupled to a model of the global pre-biotic sulfur cycle, Ranjan et al. [2023] provide plausible estimates of their prebiotic concentrations. As Sonny Harman points out in the accompanying Viewpoint, these experiments were extremely difficult to perform but provide constraints for ongoing laboratory prebiotic chemistry experiments. The authors use their model to imply that S[IV] in the ocean would have been undersaturated with respect to atmospheric SO₂, limiting the likelihood of an early persistent sulfur haze layer.

Citation: Ranjan, S., Abdelazim, K., Lozano, G. G., Mandal, S., Zhou, C. Y., Kufner, C. L., et al. (2023). Geochemical and photochemical constraints on S[IV] concentrations in natural waters on prebiotic Earth. AGU Advances, 4, e2023AV000926. https://doi.org/10.1029/2023AV000926

—Susan Trumbore, Editor in Chief, AGU Advances

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