Early Earth – Prebiotic Chemistry and Atmospheric Warming by an Active Young Sun

Australia: The Land Where Time Began

Early Earth – Prebiotic Chemistry and Atmospheric Warming by an Active Young Sun

Nitrogen is a critical ingredient of complex biological molecules (Barrett& Elmore, 1998). However, the nitrogen which was outgassed into the atmosphere of the early Earth (Ringwood, 1996) is relatively chemically inert which required high temperatures for nitrogen fixation into compounds which are chemically reactive to occur. According to Airapetian et al. possible mechanisms of nitrogen fixation include lightning, heating by atmospheric shock caused by meteorites, and ultraviolet radiation from the Sun (Summers et al., 2012; Kasting, 1990). In this paper it is shown by Airapetian et al. that nitrogen fixation in the early terrestrial atmosphere can be explained by frequent, powerful coronal mass ejection events from the young Sun, so-called superflares. In this study it was found by the use of magnetohydrodynamic simulations which were constrained by observations from the Kepler Space Telescope, that successive superflare ejections produce shocks which accelerate energetic particles, which compressed the magnetosphere of the early Earth. Pathways resulting from extended polar cap openings for energetic particles to penetrate into the atmosphere and, according to these simulations of atmospheric chemistry, initiate actions which convert molecular nitrogen, carbon dioxide and methane to nitrous oxide, which is a potent greenhouse gas, as well as hydrogen cyanide, which is an essential compound for life. Also, the destruction of N₂, CO₂ and CH₄ suggests the stability of water on the early earth cannot be explained by these greenhouse gases. Airapetian et al. propose that alternatively the efficient formation of nitrous oxide could explain a warm early Earth.

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