Atmospheric Erosion for the Terrestrial Planets: A Semi-Empirical Model
M. L. Alonso Tagle, R. Maggiolo, H. Gunell, J. De Keyser, G. Cessateur, G. Lapenta, V. Pierrard, A. C. Vandaele
Studying atmospheric erosion is a key factor to understand the evolution of planetary atmospheres and their ability to retain water, a crucial element to determine their habitability.
The solar wind interacts with planetary atmospheres, driving the loss mechanisms. Since the planets' formation, the magnetic field of the planets has significantly changed and the solar wind flux has decreased. In this study, we investigate the effects of these changes on atmospheric escape, in order to constrain the atmospheric loss over geological time scales. We present the latest development of a semi–empirical model of atmospheric erosion, for Venus-like, Earth-like and Mars-like planets. We consider seven different escape mechanisms to estimate the total atmospheric escape rate over a range of planetary magnetic moments and solar wind pressures.
We show that the escape rate peaks for high solar wind pressures on a weakly magnetized planet, contradicting the common assumption that the magnetic field of the planet protects its atmosphere from erosion. Indeed, a weakly planetary magnetized planet is associated with an intense erosion from the polar regions. Our results imply also, that when the Sun was younger and more active, the planets suffered more atmospheric loss than nowadays.
