Martian Crustal Field Influence on O⁺ and O₂⁺ Escape as Measured by MAVEN

Tristan Weber , David Brain , Shaosui Xu , David Mitchell , Jared Espley , Christian Mazelle (1) , James P. Mcfadden , Bruce Jakosky

1 IRAP - Institut de recherche en astrophysique et planétologie

Martian crustal magnetic fields influence the solar wind interaction with Mars in a way that is not fully understood. In some locations, crustal magnetic fields act as "mini-magnetospheres," shielding the planet's atmosphere, while in other locations they act as channels for enhanced energy input and particle escape. The net effect of this system is not intuitively clear, but previous modeling studies have suggested that crustal fields likely decrease global ion escape from Mars. In this study, we use data from the Mars Atmosphere and Volatile EvolutioN spacecraft to analyze how crustal magnetic fields influence both global and local ion escape at Mars. We find that crustal fields only increase ion escape if ions are not bound tightly to the magnetic field. Specifically, ion escape is increased only if closed magnetic fields trap 35% or less of energized oxygen ions. In any other case, crustal fields decrease both global and local ion escape by as much as 40% and 80%, respectively. This suggests that the presence of crustal magnetic fields has had a moderate impact on atmospheric ion loss throughout Martian history, potentially influencing the planet's atmospheric evolution and habitability.

Mots clés: Mars; ion escape; ionosphere; atmospheric escape; MAVEN; crustal magnetic fields

Domaines: Planète et Univers [physics]

Tristan Weber, David Brain, Shaosui Xu, David Mitchell, Jared Espley, et al.. Martian Crustal Field Influence on O⁺ and O₂⁺ Escape as Measured by MAVEN. Journal of Geophysical Research Space Physics, 2021, 126, ⟨10.1029/2021JA029234⟩. ⟨insu-03672408⟩