Comparing Crustal Magnetism of Terra Meridiani and Terra Cimmeria, Mars

Abstract:

Terra Meridiani displays remanent crustal magnetization, roughly symmetric and coherent over long distances, that has been interpreted by some workers as resulting from seafloor spreading. A detailed magnetization map of this region, located at 0º, 0º ±20º, will be compared with that of Terra Cimmeria (-40º, 180º) which hosts Mars' most intense and continuous magnetization. Mars Global Surveyor magnetometer (MGS MAG) data from mapping altitude (~400km) was downward continued to the surface. Data from the MGS aerobraking phase contains tracks in Terra Meridiani at altitudes between 110-190 km, revealing localized persistent B_r signatures between -268 and 278 nT, with standard deviations of 24 and 17 nT, respectively. These signatures coincide with areas of strongest magnetization on the downward continued map at corresponding altitudes. However, several uncorrelated small-scale pockets of magnetization that appear in the aerobraking dataset may be attributed to shorter wavelength signals or noise. Positive and negative sources in Terra Meridiani show comparable decay with altitude. Similarly, sources in Terra Cimmeria resemble this decay. By extrapolating into the subsurface, we estimate the source depths for both regions and observe that Terra Meridiani has shallower sources than Terra Cimmeria. The strongest magnetization in Terra Meridiani lies along the 4,600 km diameter outer ring of the Chryse basin. A similar association occurs in Terra Cimmeria along the outer rings of the Sirenum basin. The decay of magnetization intensity with altitude, crustal composition, and crustal thickness estimates will be used to create simple models of magnetic sources for Terra Meridiani.