Sprecher
Beschreibung
Photolytic Controls on Precursor Species for Prebiotic Chemistry
UV light was the dominant source of chemical free energy to the surface of early Earth by three orders of magnitude, and its e9ects have been considered for nascent organic molecules (Deamer & Weber 2010). However, far less attention has been paid to the implications of this strong chemical forcing on the inorganic chemical species invoked by prebiotic chemistry as feedstock for synthesis of these organics to begin with. I will show how UV photolysis shapes availability of prebiotic chemistry precursor species, with emphasis on sulfur and nitrogen species invoked in diverse prebiotic syntheses, (e.g., Ducluzeau et al. 2009; Becker et al. 2019; Benner et al. 2019; Xu et al. 2020). For sulfur, I will present experimental results demonstrating that while thermal disproportionation of sulfite is slow, its photolysis is fast, e9iciently converting volcanically outgassed sulfur to sulfate and restricting sulfite to trace concentrations in most prebiotic waters (Ranjan et al. 2023). For nitrogen, I will present similar results suggesting generally e9icient photolysis of nitrate, with the caveat that nitrate photolysis may have been impeded in some waters (Ranjan et al. 2019; Schuler et al., in prep). While both species were generally rare on early Earth, we show that they could potentially have built up to prebiotically relevant quantities
in shallow, closed-basin carbonate lakes. Excitingly, shallow closed-basin carbonate lakes are also predicted to have accumulated other key nutrients for prebiotic chemistry such as phosphate and nitriles, hinting towards a geologically self-consistent prebiotic chemistry (Toner & Catling 2019, 2020; Hurowitz et al. 2023). This is primarily because of the ability of such systems to evaporatively concentrate atmogenic species, and secondarily because of their ability to partially attenuate UV radiation. I will discuss the implications for proposed origin-of-life scenarios.