Decomposition of Benzene during Impacts in N₂-dominated Atmospheres

Abstract

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.

A Pulsed Hollow Cathode Discharge Operated in an Ar/N$$_2$$/O$$_2$$ Gas Mixture and the Formation of Nitric Oxide

“…A high-resolution infrared Fourier-transform spectrometer (Bruker IFS 125HR, Bruker GmBH, Karlsruhe, Germany) is operated in the mid-infrared region between 600 cm −1 and 6000 cm −1 using a KBr beamsplitter and HgCdTe liquid-N 2 -cooled detector. The measured spectra are averaged over 10 scans [63,64]. The spectra are apodized with a Boxcar apodization function and analysed using the spectr library to obtain partial pressures of the detected components [65].…”

A pulsed hollow cathode discharge operated in an Ar/N2/O2 gas mixture and the formation of nitric oxide.

“…The measured spectra are averaged over 10 scans [58,59]. The spectra are apodized with a Boxcar apodization function and analysed using the spectr library to obtain partial pressures of the detected components [60].…”

Decomposition of HCN during Experimental Impacts in Dry and Wet Planetary Atmospheres

“…Our experimental procedure combines closed, isochoric batch reactor with active gas flow, high-resolution Fourier transform infrared spectroscopy (FTIR) online detection, and analytical calibration-free data evaluation process. The experiments were performed on the ELISE experimental apparatus shown in Figure . This modular apparatus is designed for laser irradiation of samples with direct access to FTIR absorption and UV–vis emission spectroscopy for online analysis.…”

“…The parameter space of atmospheric compositions explored in this study provides a comprehensive framework for applying this chemistry to complex models of planetary atmospheres affected by impact shocks or other plasma events. In our previous research, HCN was identified as a common and significant product of the impact plasma reprocessing of planetary atmospheres. , This study centered on examining the stability of HCN in a nitrogen (N 2 ) bulk atmosphere, with variations in the initial partial pressures of HCN and H 2 O. The significant presence of N 2 aligns with dilution kinetics approaches, enhancing the experiment’s representativeness of planetary atmospheric conditions.…”

“…On the other hand, this could only be concluded assuming that no simultaneous HCN formation channels should exist during impact plasma reprocessing. When other species, such as methane or other carbohydrates, are present in the atmosphere, HCN is likely to form as well. ,, Key to further research is thus assessing the rates of impact-initiated HCN formation from methane (as the most significant source of HCN) as well as of simultaneous HCN decomposition in these conditions. We intend to address these questions in a follow-up study.…”