Thermochemical equilibrium calculations of high-temperature O2 generation on the early Earth: Giant asteroid impact on land

Abstract

Earth?s atmosphere is composed primarily of N2 and O2. The origin of free O2 in the early Earth?s atmosphere is still subject of considerable debate.1 Theoretical models suggest that the initial form of free O2 in the atmosphere has been oceanic H2O. Recent computation modeling has suggested that a superheated (ca. 2000 K) H2O vapor atmosphere of 1.4x1021 kg (the present mass of the oceans) lasting for about 3000 y could probably have been formed on Earth by an enormous (ca. 1028 J) asteroid impact. In this report, the occurrence of the thermochemical dissociation of the vapor, creating a primitive oxygenic (ca. 0.1 of the present level (PAL) of free O2) atmosphere.