Evolution of Atmospheric Oxygen Escape From Earth Since the Great Oxidation Event

This is the authors' abstract. We don't add key points for this paper.

The present study reconstructs the evolution of Earth's oxygen escape into space since the Great Oxidation Event, approximately 2450 Myr ago. We use a semi‐empirical model based on Gunell et al. (2018, https://doi.org/10.1051/0004‐6361/201832934 ) and further develop it to account for the evolution of solar wind and solar extreme ultraviolet (EUV) radiation. Seven distinct oxygen escape mechanisms are considered, and a time‐dependent escape rate is computed for each. The results show that Earth remained in a magnetized escape regime throughout the last 2450 Myr. Oxygen loss has remained dominated by nonthermal ion escape, mainly through cusp escape and polar wind. Presently, cusp escape dominates. Earlier than ∼1300 Myr ago, polar wind was the primary contributor. Oxygen ion escape is mainly driven by the solar wind and EUV radiation, limited by the ionospheric supply, and moderated by the Earth's magnetic field. Since the solar wind and solar EUV radiation were more intense in the past, the oxygen escape rate was more than an order of magnitude higher than the current value, exceeding . Over the last 2450 Myr this corresponds to a loss of ∼60% of the Earth's current atmospheric oxygen mass to space and only 0.06% of the present ocean mass. Over geological timescales, the persistence of Earth's atmospheric oxygen reservoir against escape to space is maintained by the combined effects of gravity, a strong planetary magnetic field, and a limited ionospheric supply.