One of the highlights of the Mars Global Surveyor mission was the discovery of remanent crustal magnetic anomalies on Mars. These anomalies show that Mars had at one time a strong internal global magnetic field, even though no such field exists today. Studies of the crustal anomalies, and their constraints on that ancient and now long dead main field, provide important clues about the early thermal history and crustal evolution of Mars.
Pat Taylor has been studying crustal magnetic anomalies on Earth for most of his career, first using shipborne data, then as a Magsat investigator, and most recently using Oersted and CHAMP satellite data. He has now used those same skills and approaches to study the crustal magnetic anomalies found on Mars. The journal Icarus recently accepted a paper by Taylor and co-author Jim Frawley titled Paleo-Pole Positions from Martian Magnetic Anomaly Data. In this study the two geophysicists looked for anomaly pairs on Mars that could be used to locate ancient poles for the main field that magnetized the crust and produced the anomalies. The figure at the left shows locations of 9 paleo-poles derived from their analysis of the anomaly pairs also shown. Poles are found at high northern and southern latitudes, suggesting several reversals of the main field during its believed short history. A few poles located at mid-latitudes may indicate additional excursions beyond the major reversals. Major unknowns remain, however, as to the source bodies for the anomalies and the actual nature of their magnetization.
Map showing location of the 9 crustal magnetic anomaly pairs (triangles) examined in the study, and the paleo-poles (X) derived from them. Poles at high latitudes in both hemispheres suggest reversals of the global magnetic field. This is the first finding of high latitude pale-poles among several studies of the martian anomalies. Contrary to other studies, there are no major clusters of paleo-poles at low latitudes, indicating perhaps only limited polar wander beyond reversals.
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Responsible NASA official: Dr. Herbert Frey