East–west trending magnetic anomalies in the Southern Hemisphere of Mars: Modeling analysis and interpretation

• Published in: Icarus (New York, N.Y. 1962) Vol. 191; no. 1; pp. 113 - 131
• Main Authors: Hood, Lon L., Richmond, Nicola C., Harrison, Keith P., Lillis, Robert J.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.11.2007; Elsevier
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; interior; Magnetic fields; Mars; Solar system; surface; Magnetic fields; Mars; Magnetization; Geology; surface; interior; Mars; Orbits; Southern hemisphere; Aspect ratio; MGS space probe; Radial field; Positions; Mapping manifolds; Mars; Magnetic fields; Mars; Anomaly; Models; Modelling; Solar system
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2007.04.025

Maps of the vector components of the martian crustal magnetic field over the strongly magnetized Terra Cimmeria/Sirenum region are constructed using Mars Global Surveyor magnetometer data. Although pronounced east–west trending anomalies are present on the radial and north field component maps at the mapping altitude (∼360–380 km), these trends are much less prominent at the lower aerobraking altitude (∼90–150 km). Comparisons with similar maps produced using artificial data at the aerobraking altitude indicate that elongated sources in this region may have maximum lengths along the martian surface of ∼500 km and maximum aspect ratios of ∼2. Iterative forward modeling of several relatively isolated anomalies in the mapped region yields paleomagnetic pole positions consistent with those estimated in previous studies of other anomalies using mapping phase and science phasing orbit data. On this basis, it is inferred that sources in the studied region are most probably magnetized primarily in northward or southward directions. Using this additional constraint, iterative forward modeling is then applied to determine a magnetization distribution that is consistent with data at both the aerobraking altitude and the mapping altitude. The model magnetization distribution, which includes 41 discrete sources, again indicates no highly elongated sources. An examination of surface geology in the region as well as a consideration of the global distribution of anomalies suggests that magmatic intrusions (e.g., subsurface dike swarms), cooling in the presence of water, are the most likely sources of the magnetic anomalies.