Modelling Atmospheric Erosion for Terrestrial Planets in the Solar System

Since the Great Oxidation Event, the oxygen escape rate on Earth has changed over time mainly due to solar evolution. Two solar agents drive the Earth’s atmospheric erosion rate: the solar wind and the EUV radiation. The first one affects the non-thermal processes by changing the plasma conditions, and the second one affects both types of processes: by increasing the atmospheric temperature, and by modifying the ion production rate. Hence EUV radiation affects atmospheric parameters, such as the exobase distance and neutral density, which influence the escape rate.

In this work, we describe a model that uses in-situ measurements and physical considerations to estimate the effect of solar evolution on the atmospheric loss rate. Physical assumptions are made to describe the contribution of the solar wind pressure on each erosion mechanism. The main objective is to reproduce earlier solar conditions to constrain oxygen loss over geological time scales.

Seven different mechanisms are studied, to determine the fundamental factors that have a significant impact on the oxygen escape rate in the past Earth. We discuss the effects of the exospheric parameters and solar wind drivers on the oxygen erosion rate. We examine their relevance for total oxygen loss and their influence on the stability of our atmosphere.