Potential Prebiotic Pathways in Titan’s Atmosphere: A Computational Exploration of HCN and NH3 Reactions

06 November 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


In this study, we explore the potential for prebiotic chemistry in Titan’s atmosphere through computational modeling of reactions involving hydrogen cyanide (HCN), hydrogen isocyanide (HNC), and ammonia (NH3). Our automated reaction search identifies several key intermediates, including formamidine (A), hydrazone (B), and methanediimine (C), which serve as precursors for a variety of complex organic com- pounds. Among the products, methanamine (P5) and guanidine (P22) are highlighted for their relevance to early biological activity. The calculated low activation barriers and exothermic nature of several reactions suggest the viability of these pathways in Titan’s cold environment. Notably, the formation of molecules such as a triazole derivative (P18) and N-cyanoimidoformamide (P20), linked to biomarker cyanamide, underscores the potential for synthesizing biologically significant molecules. We pro- vide theoretical roto-vibrational spectral parameters to assist in the experimental de- tection of these species, offering insights into the molecular complexity achievable in Titan’s atmosphere and contributing to our understanding of prebiotic chemistry in extraterrestrial environments.


density functional theory
prebiotic chemistry
hydrogen cyanide

Supplementary materials

Potential Prebiotic Pathways in Titan’s Atmosphere: A Computational Exploration of between HCN and NH3
In this study, we probed reactions of HCN, HNC, and NH3 to unveil pathways plausible in Titan’s atmosphere. The primary reactions, i.e., the reactions between HCN, HNC, and NH3 resulted in the generation of simpler organic compounds, formamidine (A), formaldehyde hydrazone (B), and methanedimine (C). Subsequent reactions of compounds A, B, and C with primary reactants revealed signatures of prebiotic life, producing different molecules, all containing predominantly amine, imine, or nitrile groups. We identified several molecules, such as methanamine (P5) and guanidine (P22), which are significant for prebiotic chemistry and indicative of incipient biological processes in Titan’s atmosphere. Pathway analysis for reaction viability showed promising candidates like P18 and P20, both with activation energies below 30 kcal mol−1 and favorable exothermic profiles. This implies that interactions between HCN, HNC, and ammonia could catalyze a cascade of reactions producing precursors essential for prebiotic chemistry.


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