High Energy Radical Chemistry Formation of HCN-rich Atmospheres on early Earth

Martin Ferus,Svatopluk Civiš,Petr Kubelík,Adam Pastorek,Antonín Knížek,John Sutherland

doi:10.1038/s41598-017-06489-1

Abstract

Recent results in prebiotic chemistry implicate hydrogen cyanide (HCN) as the source of carbon and nitrogen for the synthesis of nucleotide, amino acid and lipid building blocks. HCN can be produced during impact events by reprocessing of carbonaceous and nitrogenous materials from both the impactor and the atmosphere; it can also be produced from these materials by electrical discharge. Here we investigate the effect of high energy events on a range of starting mixtures representative of various atmosphere-impactor volatile combinations. Using continuously scanning time–resolved spectrometry, we have detected ·CN radical and excited CO as the initially most abundant products. Cyano radicals and excited carbon monoxide molecules in particular are reactive, energy-rich species, but are resilient owing to favourable Franck–Condon factors. The subsequent reactions of these first formed excited species lead to the production of ground-state prebiotic building blocks, principally HCN.

Highlights

Recent results in prebiotic chemistry implicate hydrogen cyanide (HCN) as the source of carbon and nitrogen for the synthesis of nucleotide, amino acid and lipid building blocks
Subsequent reactions of these species with each other and with ∙CN and other radicals (∙H and ∙NHx) do occur to some extent and produce a few larger molecules some of which are relevant in the context of the origin of life, but yields are low[10]. In this context, the efficient production of HCN in high energy chemistry of C, H, O & N containing mixtures of a wide range of composition, and its survival after cessation of high energy input are the most striking findings. Together they suggest that HCN would have been continuously produced and maintained during impact and discharge events on the early Earth
HCN can be extremely efficiently sequestered in aqueous solution by reaction with ferrous ions giving ferrocyanide[6]

Summary

Introduction

Recent results in prebiotic chemistry implicate hydrogen cyanide (HCN) as the source of carbon and nitrogen for the synthesis of nucleotide, amino acid and lipid building blocks. Based on astrochemical studies and analysis of interplanetary matter, we can expect delivery to the early Earth of simple molecules[19] such as CO, NH3, CO2, H2O, HCN, HCHO, CH3OH, and maybe HCONH222 together with complicated substances such as polymers (tholines)[23], various organic compounds and biomolecules themselves[11,24,25,26] All these molecules would be exposed to high energy plasma during descent and impact of their asteroidal or cometary vectors with the Earth and, if they survived this baptism of fire, to plasma created by subsequent impactors. Electrical discharges of lightning in heavy clouds of dust, vapours and other aerosols from impact, volcanic activity and evaporation in the early atmosphere

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Results

Conclusion