Full sphere dynamo models for Mars' ancient magnetic field

Kurzfassung

The ancient martian dynamo is mysterious in both spatial and temporal features. First, strong crustal magnetic fields are concentrated in the southern hemisphere, whereas the crustal magnetic fields in the northern hemisphere are mostly weak. Second, the ancient martian dynamo appears to have been active both before and after the Late Heavy Bombardment, with a shut down in between. These suggest that Mars’ ancient dynamo might be quite different from the conventional geodynamo. Recent seismic measurements from the NASA Mars InSight mission revealed that Mars’ core has a relatively low density, implying that it contains a larger fraction of lighter elements than previously thought. This could possibly prevent Mars from forming a solid inner core during Mars’ early history when the dynamo was active. Here we perform full sphere dynamo simulations to eliminate the influence of an inner core on dynamo behaviors. Furthermore, we investigate the effects of various heat flux perturbations at the core mantle boundary on the morphology of the resulting field and compare to models with small inner cores. These studies provide insight into Mars’ interior, thermal history and core evolution.