Mars’ Crustal Magnetic Field

Abstract

Fossil magnetic fields within the Martian crust record the history of the planet’s ancient dynamo and hence retain valuable information on the thermal and chemical evolution of Mars. In order to decode this information, we have derived a spherical harmonic model of the crustal magnetic field. This model was derived from satellite vector magnetometer data, and allows to study the crustal magnetic field at high resolution down to surface altitudes. Based on this model, we calculate the required magnetization of the Martian crust, and discuss how the resulting strong magnetization might be explained. Further, we study the magnetization of impact craters and volcanoes, and conclude that the Martian core dynamo shut down most probably in the Noachian, at about 4.1 Gyr ago. Finally, we address the derivation of magnetic paleopole positions. In a first step, we use synthetic tests in order to outline under which constraints paleopole positions can be determined from satellite measurements. In a second step, we use these insights to present a scheme to estimate paleopole positions including an assessment of their underlying uncertainties.