The influence of degree-1 mantle heterogeneity on the past dynamo of Mars

Research areas:
Phys. Earth Planet. Int.
The hemispheric dichotomy in the crustal magnetic
field of Mars may indicate that the planet's past
dynamo was influenced by a degree-1 heterogeneity on
the outer boundary of its liquid metallic convecting
core. Here we use numerical dynamos driven by purely
volumetric internal heating with imposed degree-1
heat flux heterogeneities to study mantle control on
the past dynamo of Mars. We quantify both
south~north and east~west magnetic field dichotomies
from time-average properties that are calculated
according to two different end member crust
formation scenarios. Our results indicate that a
moderate heat flux anomaly may have been suf~cient
for obtaining the observed dichotomy. Because of the
excitation of a strong equatorial upwelling in the
dynamo, the ef~ciency of a mantle heterogeneity
centered at the geographical pole in producing a
south~north dichotomy is much higher than that of an
heterogeneity centered at the equator in producing
an east~west dichotomy. These results argue against
a significant True Polar Wander event with major
planet reorientation after the cessation of the