Experimental simulations of cosmic impacts on rubrene nanoparticles in the water environment reveal the potentiality of condensed phases of polycyclic aromatic hydrocarbons to generate prebiotic molecules

Abstract

Organic compounds, such as the polycyclic aromatic hydrocarbons (PAHs), are among the major species responsible for the infrared spectral features characterising the cosmic background radiation. Similar to silicate dust, aggregates rich in carbon with micro- and nano-meter sizes are subjected to several weathering processes in various astrophysical environments that modify their chemistry and structure, thus contributing to the chemical richness of the cosmic environment. In particular, the study of the chemical and structural evolution of PAHs aggregates in the presence of water is relevant to understand the mechanism of formation of the prebiotic building blocks of life.Pulsed laser ablation of a water-dispersed nano-phase of rubrene (5,6,11,12-tetraphenyltetracene) is here performed to reproduce the high energy-density conditions occurring in shock events in the interstellar medium, while ensuring the presence of a water environment. We studied the structural and chemical evolution of the dispersed rubrene nanocrystals upon laser treatment, showing that rubrene undergoes a fragmentation process producing water soluble species. The results obtained demonstrate that the extreme conditions occurring in cosmic environments coupled with the presence of water are sufficient conditions for transforming PAHs into prebiotic molecules.