Stellar irradiation is thought to be a significant contributor to the origin of life. Ultraviolet (UV) light interacting with iron cyanide complexes may play an important role in prebiotic chemistry. The UV-Visible (UV-Vis) spectra of these iron cyanide complexes can be measured by the same source that drives the chemistry, providing a real-time in-situ quantitative analysis of prebiotically relevant UV-driven photochemistry. We measure the UV-Vis absorbance of ferrocyanide and nitroprusside, and relate this absorbance to known concentrations. We show that these absorbances can be combined to accurately predict the concentrations of ferrocyanide-nitroprusside mixtures that could be generated from ferrocyanide and nitroxyl salts irradiated by ultraviolet light. The ferrocyanide molar attenuation coefficients were found to be: epsilon₅₄ₑₑ₎₂ₘ₀₍₈₃₄ (340 nm) = (2. 2 +/- 0. 4) x 10³ dm² mol^-1. Nitroprusside peaks show the following values: epsilon₍₈ₓₑ₎ₑₔₒₒ₈₃₄ (340 nm) = (4. 1 +/- 0. 3) x 10² dm² mol^-1, epsilon₍₈ₓₑ₎ₑₔₒₒ₈₃₄ (400 nm) = (1. 71 +/- 0. 05) x 10² dm² mol^-1, and epsilon₍₈ₓₑ₎ₑₔₒₒ₈₃₄ (500 nm) = 62. 1 +/- 1. 7 dm² mol^-1. With the help of our measured absorbances, we consider ferrocyanide and nitroprusside as sunscreens. In the absence of extra ferrocyanide sources, UV-sensitive compounds could be protected on timescales of months. This would allow for compounds like nicotinamide adenine dinucleotide, NADH, to survive for over a year at depths of 5 m, compared to a lifetime of 6 months when unprotected. Our toy model constrains the photochemical survival of compounds of interest to the origin of life community across a comprehensive spectral range and can be used to constrain the survival using different exoplanetary irradiative conditions; thus exploring the UV environment with the presence of ferrocyanide and nitroprusside and contributing to the wider discussion surrounding the prevalence of the origin of life in the Universe.
Rossmanith et al. (Thu,) studied this question.