An improved crustal magnetic field map of Mars from electron reflectometry: Highland volcano magmatic history and the end of the martian dynamo

摘要: Abstract We apply improved kinetic modeling of electron transport in the martian thermosphere to fit pitch angle distributions measured by Mars Global Surveyor (MGS) Magnetometer/Electron Reflectometer (MAG/ER), together with appropriate filtering, binning, averaging and error correction techniques, create most reliable ER global map date crustal magnetic field magnitude at 185 km altitude, twice spatial resolution considerably higher sensitivity fields than maps components produced MAG data alone. This compares favorably sparsely sampled dayside taken similar altitudes, insofar as a direct comparison is meaningful. Using this map, we present two case studies. The first signatures highland volcanoes, concluding that comparatively greater thermal demagnetization Syrtis Major compared Tyrrhena Patera likely due ratio intruded extruded magmas. second uses along topographic compare crater retention ages demagnetized Hellas impact basin magnetized Ladon basin. From comparison, determine dynamo went from substantial very weak or nonexistent absolute model age time interval 4.15 ± 0.05 4.07 Ga ago.