Mars' Hemispheric Magnetic Field From a Full-Sphere Dynamo

Seismic measurements from the NASA Mars InSight mission revealed that Mars’ core has a relatively low density, implying a larger fraction of lighter elements than previously thought, which further leads to a low melting temperature. Thus, Mars probably never developed a solid inner core during its early history when the dynamo was active. We perform full-sphere dynamo simulations to eliminate the influence of an inner core on dynamo behaviors and investigate how various magnitudes of heat flux perturbations at the core-mantle boundary affect the field morphology, comparing results to those from models with small inner cores. We find that a hemispheric magnetic field can result when the heat flux is concentrated in one hemisphere. Moreover, a dynamo model without the presence of an inner core can better explain Mars’ crustal magnetic field dichotomy than that in a spherical shell surrounding a solid inner core.