2023ApJ...945..149P

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N₂-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C₂H₂, and smaller amounts of CH₄ with yields of 3.1%-24.0%, 0-11.7%, and 0.5%-3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO₂ with yields of 2.4%-35.1% and 0.01%-4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N₂-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C₂H₂, and CH₄ and, in the presence of water, to the formation of CO and CO₂.