Evolution of the oxygen escape from Earth over geological time scales

Abstract

Atmospheric erosion plays a significant role in the long-term evolution of planetary atmospheres, and therefore on the development and sustainability of habitable conditions. Atmospheric escape varies over time, due to changes in planetary conditions and the evolution of the Sun. In the case of a magnetized planet like Earth, the dominant scavenging mechanisms are polar wind and polar cusp escape. Both processes are sensitive to the ion supply from the atmosphere, which depends on the solar EUV radiation and the composition of the neutral atmosphere. Moreover, they are modulated by the coupling between the solar wind and the ionosphere, which depends on the solar wind dynamic pressure and the planetary magnetic moment.We developed a semi-empirical model of atmospheric loss to extrapolate from current measurements of oxygen escape from Earth to past conditions. This model takes into account the variations of the solar EUV/UV flux, the solar wind dynamic pressure, and the Earth’s magnetic moment. In this study, we identify the main factors and processes that control oxygen escape from Earth, considering present-day atmospheric conditions. We constrain the variation of the oxygen loss rate over time and estimate the total oxygen loss during the last ~2 billion years.