Title: A spatially continuous magnetization model for Mars

Author(s): Whaler KA, Purucker ME

Source: JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 110 (E9): Art. No. E09001 SEP 2 2005

Document Type: Article

Language: English

Abstract: Using a three-component magnetic field data set at over 100,000 satellite points previously compiled for spherical harmonic analysis, we have produced a continuously varying magnetization model for Mars. The magnetized layer was assumed to be 40 km thick, an average value based on previous studies of the topography and gravity field. The severe nonuniqueness in magnetization modeling is addressed by seeking the model with minimum root-mean-square (RMS) magnetization for a given fit to the data, with the trade-off between RMS magnetization and fit controlled by a damping parameter. Our preferred model has magnetization amplitudes up to 20 A/m. It is expressed as a linear combination of the Green's functions relating each observation to magnetization at the point of interest within the crust, leading to a linear system of equations of dimension the number of data points. Although this is impractically large for direct solution, most of the matrix elements relating data to model parameters are negligibly small. We therefore apply methods applicable to sparse systems, allowing us to preserve the resolution of the original data set. Thus we produce more detailed models than any previously published, although they share many similarities. We find that tectonism in the Valles Marineris region has a magnetic signature, and we show that volcanism south of the dichotomy boundary has both a magnetic and gravity signature. The method can also be used to downward continue magnetic data, and a comparison with other leveling techniques at Mars' surface is favorable.

KeyWords Plus: SPHERICAL HARMONIC MODEL; MERIDIANI-PLANUM; CRUSTAL MAGNETIZATION; SATELLITE DATA; HIGH-ALTITUDE; FIELD; ANOMALIES; MAGNETISM; HEMATITE; GRAVITY

Addresses: Whaler KA (reprint author), Univ Edinburgh, Sch Geosci, Inst Earth Sci, W Mains Rd, Edinburgh, Midlothian EH9 3JW Scotland
Univ Edinburgh, Sch Geosci, Inst Earth Sci, Edinburgh, Midlothian EH9 3JW Scotland
NASA, Goddard Space Flight Ctr, Planetary Geodynam Lab, Raytheon ITSS, Greenbelt, MD 20771 USA

E-mail Addresses: kathy.whaler@ed.ac.uk, purucker@geomag.gsfc.nasa.gov

Publisher: AMER GEOPHYSICAL UNION, 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA

Subject Category: GEOCHEMISTRY & GEOPHYSICS

IDS Number: 962JR