An Explosive Leakage of Heavy Ions From Martian Crustal Magnetic Anomalies

Abstract

Atmospheric escape processes are crucial for shaping the long-term surface habitability of terrestrial planets. A key question is how planetary magnetic fields influence atmospheric escape. On present-day Mars, there are crustal magnetic anomalies predominantly in the southern hemisphere, whose impact on the escape of ionospheric heavy ions remains under debate. Based on MAVEN observations, we propose a new candidate mechanism to explain how ionospheric heavy ions can escape from regions with strong crustal magnetic anomalies. This mechanism is triggered by reconnection between draped interplanetary and crustal magnetic fields, forming magnetic cusps with open field lines and generating plasma jets that impact the crustal anomalies. Within these anomalies, ions and electrons exhibit distinct spatial and temporal behaviors, leading to charge separation and the formation of an electrostatic potential. This potential lifts cold, heavy ions from the ionosphere along open field lines to escape altitudes. The process occurs within minutes, producing localized escape fluxes up to two orders of magnitude higher than background levels. This explosive leakage pattern may hold significance for other unmagnetized or weakly magnetized planets where magnetospheric and ionospheric boundaries converge.