High-energy chemistry of formamide: A unified mechanism of nucleobase formation

Abstract

The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules.

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

“…The formation of acids 29-32 may be explained by the in situ generation of HCN followed by oligomerization to DAMN (actually detected in the reaction mixture), hydrolysis, and successive redox processes (112). Moreover, carboxylic acids have been also produced in low amount during UV photoprocessing of interstellar ice analogs (113), i.e., by slow deposition of simple mixtures of CO, NH 3 , and H 2 O, with formation, among others, of 30 and 32 (114). In this latter case, radical mechanisms involving nitrogen and carbon-centered species have been hypothesized (115).…”

“…FA (NH 2 CHO) is becoming one of the most intensively studied precursors for prebiotic syntheses of compounds potentially relevant for the origin of life (1)(2)(3)(4). FA is a ubiquitous molecule in the universe.…”

“…Evidence of the catalytic properties of meteorites in prebiotic chemistry was recently provided by thermal processes of condensed-phase FA at relatively high temperatures (333 and 413 K) (57,58) or at the most extreme temperature conditions modeling impact events in Earth's atmosphere or surface (3,59). During their wandering, meteorites are exposed, under an extreme variety of temperature conditions, to ionizing radiation of cosmic origin (60) able to excite and dissociate FA (the ionization energy of the FA being ∼11-15 eV).…”

Heuristic Approach to Understanding the Accumulation Process in Hydrothermal Pores

“…On the early earth, the estimated formamide concentrations were fairly low of the order of 10 −7 -10 −3 wt % [3][4][5][6][7][8]33]. The highest concentrations were probably reached in lakes with depths of up to 10 m. In these regions, the formamide concentration increased because of preferential vaporization of water, with a roughly two times lower boiling point compared to formamide [4].…”

“…Formamide has been discussed as an educt for the formation of prebiotic molecules for almost 50 years [3][4][5][6][7][8]. Saladino et al synthesized all nucleobases from concentrated aqueous FA solutions [5].…”