Nov 22 – 25, 2021
Kloster Irsee,
Europe/Berlin timezone

Ferrocyanide survival under near ultraviolet (300-400 nm) irradiation on the early Earth

Nov 23, 2021, 5:05 PM
Kloster Irsee,

Kloster Irsee,


Zoe Todd (U. of Washington, Seattle)


Prebiotic lake environments containing ferrocyanide could have fostered origins of life chemistry on the early Earth. Ferrocyanide, coupled with sulfite or sulfide, can participate in an ultraviolet (UV)-driven photoredox cycle to generate solvated electrons, which can reduce cyanide to form all four major building blocks of life: sugars, amino acids, nucleotides, and lipid precursors. However, longer wavelength UV light (~300-400 nm) causes photoaquation of ferrocyanide into pentacyanoaquaferrate, Fe(CN)5H2O. This species can either regain cyanide to reform ferrocyanide or ultimately lose cyanide ligands, which removes ferrocyanide from solution. Here, we investigate this longwave (300-400 nm) UV-driven loss of ferrocyanide. In addition to determining the wavelength dependence of the loss and the implications from the UV environment on the early Earth, we also study the effects of pH, temperature, and concentration. We find that in dilute, slightly alkaline solutions, ferrocyanide would degrade significantly on the order of minutes under the longwave UV radiation expected on the early Earth. We further determine that the lifetime of ferrocyanide is extended at more alkaline pH, lower temperatures, and higher concentrations. Under a reasonable set of planetary conditions, we find that ferrocyanide lifetimes in irradiated environments range from minutes to hours. Our results can help to determine the constraints implied by the UV-driven loss of ferrocyanide in prebiotic environments. We assess the potential environmental limits and circumstances that would allow for successful retention of significant amounts of ferrocyanide in prebiotic lakes, with the goal of aiding the construction of consistent and plausible circumstances for prebiotic chemistry on the early Earth.

Presentation materials