The interstellar origin and chemistry of the NCN moiety, a critical molecular backbone of nucleobases, is central to the RNA world hypothesis for the Origins of Life; however, its formation mechanisms under astrophysical conditions remain largely unexplored. Here, we report the first laboratory preparation of cyanamide (NH2CN), a key intermediate in prebiotic chemical evolution, in low-temperature ammonia-methylamine (NH3-CH3NH2) interstellar ice analogs exposed to energetic electrons, simulating secondary electrons generated by galactic cosmic rays. Utilizing tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry combined with isotopic labeling, cyanamide was identified isomer-selectively in the gas phase during temperature-programmed desorption. These findings reveal nonequilibrium pathways to cyanamide in methylamine-containing interstellar ices, highlighting the pivotal role of galactic cosmic rays in forming the biorelevant NCN backbone and shedding light on the abiotic synthesis of nucleobases in astrophysical environments.
Wang et al. (Mon,) studied this question.