Geodynamics Science Highlight
NASA GSFC Geodynamics 921

SCIENCE HIGHLIGHT

Geodynamics Branch, Code 921

January 2003

Langlais Study Compares Mars Magnetic Anomalies with Craters:
New Model of Mars Magnetic Field Combines High and Low Data Shows Improved Spatial and Amplitude Resolution

Benoit Langlais, a Resident Research Associate in the Geodynamics Branch, has produced a new model of the martian magnetic field. This model was derived from 28 months of data from the Mars Global Surveyor, and used the equivalent dipole approach, a technique often employed since its early application to MAGSAT data in the 1980’s. In the current model, Langlais determined magnetiza- tion directions and used all three of the measured components. The dipoles are assumed to be 40 km thick, with a most likely depth of about 20 km below the mean radius of the planet.

Magnetization components, assuming a 40 km thick layer at 20 km depth, shown with impact craters with diameter larger than 300 km. Magnetization components, assuming a 40 km thick layer at 20 km depth, shown with impact craters with diameter larger than 300 km.

A global model, based on measurements made between 80 and 430 km altitude, resulted in a best mean resolution of 173km. The rms residuals between observations and predictions are as low as 15 nT for the total field, with a correlation coefficient of 0.97. The resulting model was used to predict the magnetic field at 200 km constant altitude, for studies of possible crustal sources. For the assumed 40 km thick magnetized layer, the magnetization range is +/- 12 A/m.

Among the interesting results is the apparent lack of any magnetic signatures for craters larger than about 300 km (see Figure), not just for the very large basins like Hellas and Argyre. Likewise, the major volcanic features have no associated anomalies.

Contact: Benoit Langlais, GSFC, Code 921 (langlais@ltpmail.gsfc.nasa.gov)

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Responsible NASA official: Dr. Herbert Frey

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Last modified on Jan 21, 2003