Thermochemical equilibrium calculations of high-temperature O_2 generation on the early Earth: Giant asteroid impacts on land

摘要

Earth's atmosphere is composed primarily of N_2 and O_2. The origin of free O_2 in the early Earth's atmosphere is still subject of considerable debate. Theoretical models suggest that the initial form of free O_2 in the atmosphere has been oceanic H_2O. Recent computation modelling has suggested that a superheated (ca. 2000 K) H_2O vapor atmosphere of 1.4x 10~(21) kg (the present mass of the oceans) lasting for about 3000 y could probably have been formed on Earth by an enormous (ca. 10~(28) 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 O_2) atmosphere.