Potential Prebiotic Pathways in Extraterrestrial Atmosphere: A Computational Exploration of HCN and NH₃ Reactions

Abstract

In this study, we explore the potential for prebiotic chemistry in an extraterrestrial atmosphere through computational modeling of reactions involving hydrogen cyanide (HCN), hydrogen isocyanide (HNC), and ammonia (NH 3 ). Based on our automated reaction search, we identified several key intermediates, including formamidine (A), formaldehyde hydrazone (B), and methanediimine (C) which serve as precursors for a variety of complex organic compounds. Among the products, methanimine (P5) and guanidine (P22) have been proposed 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 a cold extraterrestrial 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 provide theoretical roto-vibrational spectral parameters to assist in the experimental detection of these species, offering insights into the molecular complexity achievable in extraterrestrial atmosphere and contributing to our understanding of prebiotic chemistry in extraterrestrial environments.

A Thermodynamic Landscape of Hydrogen Cyanide-Derived Molecules and Polymers

“…21 We consider here consider a selection of pure HCN-based materials, i.e., structures where the stoichiometry of H, C and N are 1:1:1 (and no additional elements). Other HCN-based materials can incorporate oxygen, 12 additional nitrogen and hydrogen 22 or form through condensation reactions, e.g., through the formation of NH3. 12,18,23,24 Such materials, which may also be important, are beyond the scope of this work.…”

A Thermodynamic Landscape of Hydrogen Cyanide-Derived Molecules and Polymers

“…We here consider a selection of pure HCN-based materials, i.e., structures where the stoichiometries of H, C, and N are 1:1:1 (and no additional elements). Other HCN-based materials can incorporate oxygen, additional nitrogen, and hydrogen or form through condensation reactions, e.g., through the formation of NH 3 . ,,, Such materials, which may also be important, are beyond the scope of this work. In the following, we will first introduce the materials we study and then proceed to evaluate their relative thermodynamic stability.…”