Sensitivity of the ancient martian dynamo to hemispheric CMB heat flux patterns

Abstract:

Magnetic field observations from the Mars Global Surveyor, MAVEN, and InSight missions reveal that a dynamo was active in Mars’ early history. One unique feature of Mars’ crustal field is its hemispheric dichotomy, with the southern hemisphere crustal fields stronger than those in the northern hemisphere. The hemispheric dichotomy has been previously proposed to be due to either crustal reprocessing or a hemispheric dynamo.

Here we use numerical dynamo models to investigate the potential hemispheric nature of Mars’ ancient dynamo. Previous studies show that a hemispheric heat flux perturbation at the core-mantle boundary could result in either a stable hemispherical magnetic field or a constantly reversing field, depending on the choices of parameters used in the models. These two scenarios lead to very different implications for the generation of crustal fields. Here we test the dynamo sensitivity to various heat flux perturbations at the core-mantle boundary in a broader parameter regime than previous studies in order to understand whether a hemispheric dynamo is likely for early Mars. We also compare to constraints available on the martian crustal field intensity determined from the InSight mission.