The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic

Abstract

This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N + CH mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO reactivity. CO was introduced to the standard N + CH mixture at different mixing ratio up to 5 % CH and 3 % CO. The reaction products were characterized by FTIR spectroscopy. This work shows that CO modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO on increasing concentration other products as cyanide (HCN) and ammonia (NH).

Analysis of the products of a negative corona discharge in a N2–CH4 mixture with added CO2 used as a laboratory mimic of a prebiotic atmosphere

“…Ramirez et al used both negative and positive corona discharges in a wire–cylinder configuration at a pressure of 650 mbar and temperature of 298 K with a mixture of 2–10% methane in nitrogen. The energy yield determined in their experiment for HCN is about one order lower than the value determined in this study; however, Ramirez et al did not study any CO 2 mixtures, which can increase the HCN concentration . They also observed an energy yield of 2.0 × 10 14 J −1 for HCN in a positive corona discharge.…”

“…Mazankova et al used an abnormal glow discharge operating at atmospheric pressure and at a temperature of 300 K. The specific input energy in their study was in the range 6–17 J/mL, which is higher than in this study using a corona discharge; however, the energy yields calculated from their data agree well with those obtained in this study. Indeed, the energy yield for NH 3 is the same in both discharges, although the electrode surface for the corona discharge is much lower than the surface of electrodes used for the glow discharge.…”

“…The main reactions for the creation of HCN, C 2 H 2 , and NH 3 in N 2 + CH 4 mixtures have been described in previous studies . The increase in CO concentrations can be attributed to the reaction which also produces H 2 CO .…”

“…The bands corresponding to CH 4 had negative absorbance, which means that the CH 4 concentration decreased as a result of dissociation and ionization in the discharge. HCN, which has been recognized as the most abundant product in N 2 + CH 4 atmospheres, was clearly identified by the absorption peaks at 3,311 cm −1 (CH stretching v 1 ) and 712 cm −1 (bend v 2 ) . The HCN density was determined using the band around 3,311 cm −1 (Figure a).…”

“…The effect of an electric discharge on highly reducing gas mixtures of methane (CH 4 ), nitrogen (N 2 ), and ammonia (NH 3 ) with water vapour has been shown to result in the synthesis of many different biologically important organic compounds including amino acids . It has been also shown that ammonia can be produced in discharges at atmospheric pressure and it is assumed that ammonia can be created by reactions on surfaces . Such electrical discharges are believed to imitate the effect of thunderstorm lightning on chemical processes in prebiotic atmospheres; indeed, the Miller–Urey spark discharge experiments in the early 1950s were the first experimental studies describing the results in reducing atmospheres and led to the start of laboratory studies of the origins of prebiotic material on the Earth.…”