Organic chemistry in a CO2 rich early Earth atmosphere

TL;DR

This study investigates how ionospheric chemistry driven by early Earth's VUV radiation could produce complex organic molecules from CO2, suggesting a potential endogenous pathway for prebiotic organic synthesis.

Contribution

It demonstrates experimentally that ionospheric chemistry in early Earth conditions can generate complex organic compounds from CO2, N2, and H2, highlighting a new endogenous prebiotic pathway.

Findings

Formation of water, ammonia, N2O, and C2N2 detected

Solid organic phase with nitrogenous functions observed

Ionospheric chemistry can produce prebiotic organics from CO2

Abstract

The emergence of life on the Earth has required a prior organic chemistry leading to the formation of prebiotic molecules. The origin and the evolution of the organic matter on the early Earth is not yet firmly understood. Several hypothesis, possibly complementary, are considered. They can be divided in two categories: endogenous and exogenous sources. In this work we investigate the contribution of a specific endogenous source: the organic chemistry occurring in the ionosphere of the early Earth where the significant VUV contribution of the young Sun involved an efficient formation of reactive species. We address the issue whether this chemistry can lead to the formation of complex organic compounds with CO2 as only source of carbon in an early atmosphere made of N2, CO2 and H2, by mimicking experimentally this type of chemistry using a low pressure plasma reactor. By analyzing the gaseous phase composition, we strictly identified the formation of H2O, NH3, N2O and C2N2. The formation of a solid organic phase is also observed, confirming the possibility to trigger organic chemistry in the upper atmosphere of the early Earth. The identification of Nitrogen-bearing chemical functions in the solid highlights the possibility for an efficient ionospheric chemistry to provide prebiotic material on the early Earth.