Origin of precursors of organic molecules during evaporation of meteorites and mafic terrestrial rocks

Abstract

THE accretion of the Earth was characterized by high-temperature transformations of planetesimal matter during high-velocity impacts. In the final stages of the Earth's growth, up to 30% of planetesimal mass and the corresponding mass of the target were evaporated^1-3. Here we look at the effect of laser-pulse heating on meteorite materials and silicates in order to simulate the vaporization which occurs during impacts and to study the chemical composition of the gases produced. In our experiments, the residual gas mixture consisted of both oxidized and reduced components: CO, CO₂, SO₂, H₂O, H₂, N₂, H₂S, COS, CS₂, various hydrocarbons from C₁ to C₆, HCN and CH₃CHO. In addition, we find that the composition of the gas mixtures is qualitatively similar for all samples. Our data give an idea of the chemical composition of gases that may have been released into the Earth's early atmosphere by impact devolatilization. In the gas mixtures produced by these experiments we measured weight per cents of ∼10⁻³ for HCN, ∼10⁻⁴ for CH₃CHO and ∼10⁻² for hydrocarbons. Impact vaporization is no less effective for the formation of HCN than is the formation of HCN by impact reprocessing of the atmosphere⁴. For the production of aldehyde and hydrocarbons, impact vaporization is even more effective. The gas mixtures formed by vaporization of silicates provide favourable conditions for abiotic synthesis of organic compounds.