Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmgp72a1000s&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #GP72A-1000
Physics
1517 Magnetic Anomaly Modeling
Scientific paper
The magnetization of ALH84001 and the origin of its magnetic carriers have implications for the martian dynamo and the crustal anomalies on Mars. It is now evident that the magnetization of ALH84001 is predominantly carried by single domain magnetite, which formed by thermal decomposition of siderite at elevated temperature in a major impact event at about 4.0 Gyr. Saturation remanent magnetization normalization of the intensity of magnetization of ALH84001 suggests that the ambient field at 4.0 Gyr, in which NRM was acquired, was one order of magnitude weaker than the present geomagnetic field. Since the generating volume for the martian field is smaller than that of the earth, it is unlikely that the field was ever orders of magnitude greater than the geomagnetic field, or even substantially greater than the value interpreted at 4.0 Gyr. Surprisingly, the measured martian anomalies are an order of magnitude larger than anomalies observed on earth at comparable satellite altitudes. This implies that the martian crust contains substantial volumes of source rock more strongly magnetized than found in comparable volumes on earth. The most potent plausible magnetic phase is single domain (SD) magnetite of which about 1 part in 100 in source regions would suffice. We suggest that SD magnetite formed as a result of thermal decomposition of siderite in altered iron rich basaltic rocks. Experiments and theory show that siderite is a major product of percolation and evaporation of brines generated under pressures of more than 0.1bar of carbon dioxide. This is the preferred explanation for the carbonate in nakhlites, as well as in ALH84001. Thermal decomposition of siderite may result from deep burial, magmatic heat sources, or impact heating. The model predicts that conditions in the northern hemisphere of Mars precluded the formation of SD magnetite by the decomposition of siderite, and for this reason the stronger anomalies are confined to the southern highlands.
Fuller Michael M.
Scott Edward
No associations
LandOfFree
Magnetization of ALH84001: Inferences for the Martian Magnetic Anomalies. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Magnetization of ALH84001: Inferences for the Martian Magnetic Anomalies., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetization of ALH84001: Inferences for the Martian Magnetic Anomalies. will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1892522