Nucleobase synthesis in interstellar ices

Abstract

The synthesis of nucleobases in natural environments, especially in interstellar molecular clouds, is the focus of a long-standing debate regarding prebiotic chemical evolution. Here we report the simultaneous detection of all three pyrimidine (cytosine, uracil and thymine) and three purine nucleobases (adenine, xanthine and hypoxanthine) in interstellar ice analogues composed of simple molecules including H2O, CO, NH3 and CH3OH after exposure to ultraviolet photons followed by thermal processes, that is, in conditions that simulate the chemical processes accompanying star formation from molecular clouds. Photolysis of primitive gas molecules at 10 K might be one of the key steps in the production of nucleobases. The present results strongly suggest that the evolution from molecular clouds to stars and planets provides a suitable environment for nucleobase synthesis in space.

Neural-network assisted study of nitrogen atom dynamics on amorphous solid water – I. adsorption and desorption

“…The formation of the simplest molecule, H 2 , can be exclusively explained considering surface processes (Cuppen et al 2017). However, surface chemistry in space is not limited to the archetypal H 2 formation and the amount of possible chemical paths in surfaces increases constantly, determined both experimentally (Kobayashi et al 2017;Fedoseev et al 2017;Qasim et al 2019;Potapov et al 2019;Oba et al 2019;Potapov et al 2020) and theoretically (Enrique-Romero et al 2016;Meisner et al 2017;Rimola et al 2018;Molpeceres et al 2019;Lamberts et al 2019). The composition of solid bodies (known as dust grains) in the interstellar medium depends on the temperature conditions of each particular astronomical object and the nature of the parent star.…”

Spectroscopic identification of fragment ions of DNA/RNA building blocks: the case of pyrimidine

“…37,38 It has been proposed that such N-containing macromolecules may be synthesized through complex reactions between abundant N-bearing species such as NH 3 or HCN and carbonaceous precursors in interstellar ice grains under the influence of UV photons and cosmic ray analogs (e.g., protons and electrons). [39][40][41][42][43] Recent laboratory experiments under interstellar-like conditions demonstrate the formation of uracil and cytosine upon UV irradiation of H 2 O:Pym and H 2 O:NH 3 :Pym ices, respectively. 44,45 These experiments triggered theoretical investigations to gain further insight into the involved chemical conversion scheme.…”

Extraterrestrial hexamethylenetetramine in meteorites—a precursor of prebiotic chemistry in the inner solar system

“…In the present study, we extracted relatively large portions (masses ranging from 0.5 to 2 g) of interior samples of three carbonaceous chondrites, Murchison, Murray, and Tagish Lake, under mild conditions which utilized neither concentrated acidic solutions nor high temperatures for the extraction processes. The aqueous extracts were purified using cation-exchange chromatography and were then analysed using a high-resolution mass spectrometer (HRMS) coupled with a highperformance liquid chromatograph (HPLC) 19,25 . HMT was successfully detected from Murchison, Tagish Lake, and Murray meteorite extracts at parts-per-billion levels.…”