The escape of molecular hydrogen and the synthesis of organic nitriles in planetary atmospheres

Abstract

What is the influence of hydrogen escape from the atmosphere of small planetary bodies on the synthesis of organic molecules in that atmosphere? To answer this question, laboratory experiments have been performed to study the evolution of different reducing model atmospheres submitted to electrical discharges, with and without the simulation of H 2 escape. A study of mixtures of nitrogen and methane shows a very strong effect of H 2 escape on the formation of organic nitriles, the only nitrogen containing organics detected in the gas phase. These are HCN, CH  CCN, (CN) 2, CH 2CHCN, CH 3 CN and CH 3CH 2CN. The yield of synthesis of most of these compounds is noticeably increased, up to several orders of magnitude, when hydrogen escape is simulated. The escape of H 2 from the atmosphere of the primitive Earth may have played a crucial role in the formation of reactive organic molecules such as CHCCN or (CN) 2, which can be considered as important prebiotic precursors. These experimental results may also explain extant data concerning the nature and relative abundance of organics present in the atmosphere of Titan, a planetary satellite which may be an ideal model within our solar system for the study of organic cosmochemistry and exobiology.