HR: 12:05h
AN: GP21D-08    [PDF]
TI: A Polar Magnetic Paleopole on Mars?
AU: * Langlais, B
EM: langlais@ltpmail.gsfc.nasa.gov
AF: NAS/NRC at GSFC/NASA, Geodynamics Branch, code 921, Greenbelt, MD 20771 United States
AU: * Langlais, B
EM: langlais@ltpmail.gsfc.nasa.gov
AF: Universit{\'e} de Nantes, Laboratoire de Plan{\'e}tologie et G{\'e}odynamique, 2 rue de la Houssini{\`e}re, BP 92208, Nantes, 44000 France
AU: Purucker, M
EM: purucker@geomag.gsfc.nasa.gov
AF: Raytheon/ITSS at GSFC/NASA, Geodynamics Branch, code 921, Greenbelt, MD 20771 United States
AB: A global map of the Martian magnetic field is computed using MGS magnetic measurements and an equivalent source approach. Sources are located arbitrarily (i.e. with a constant spacing) near the surface of Mars. The magnetic field and the magnetization (from the equivalent source solution) present similar features: magnetic anomalies are mostly located South of the crustal dichotomy, the largest craters as well as the largest volcanoes of the North hemisphere do not seem to present any significant magnetic anomaly. In one case at least, a volcanic edifice, Apollinaris Patera, seems to be associated with a magnetic anomaly. This volcano is located at (9.3$^\circ$S, 174.4$^\circ$E), North of Terra Cimmeria and Terra Sirenum, where the largest magnetic anomalies were detected. It rises about 5 km above the surrounding terranes. Its shape is a 200-km wide dome, with a 75-km wide caldera on its submit. This is one of the largest volcanoes in the Southern Hemisphere. It is associated with a relatively high gravity anomaly. Crater counts and stratigraphic relations suggest a middle Hesperian age for its younger flow, but it presumably had a long history. We present the modeling of the magnetic anomaly located above this volcano. We use a single equivalent source, located below the volcano. The direction of the magnetization of the source leads to a polar position (70$^\circ$ latitude) for the paleopole. Assuming that the last eruptive stages occurred while the Martian dipolar dynamo was still active, then this paleopole position would indicate that the Martian magnetic field was almost aligned on the present day rotation axis of the planet.
DE: 1517 Magnetic anomaly modeling
DE: 5440 Magnetic fields and magnetism
DE: 6225 Mars
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting