Tectonic implications of Mars crustal magnetism

1. 

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   Fig. 1.

   Map of the magnetic field of Mars observed by the MGS satellite at a nominal 400-km altitude. Each pixel is colored according to the median value of the filtered radial magnetic field component observed within the 1° × 1° latitude/longitude range represented by the pixel. Colors are assigned in 12 steps spanning two orders of magnitude variation. Where the field falls below the minimum contour, a shaded Mars Orbiter Laser Altimeter topography relief map provides context. Contours of constant elevation (–4, –2, 0, 2, and 4 km elevation) are superimposed, as are dashed lines representing rotations about common axes (short dashed line, axis northeast of Elysium Mons; long dashed line, axis northeast of Hellas).

   
   
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   Fig. 2.

   Magnetic field map of Terra Meridiani, as in Fig. 1 but centered on the zero meridian. Dashed lines indicate parallel great faults drawn as small circles about a common rotation axis (+) intersecting the sphere northeast of Hellas (23°S, 83.5°E). The white line marks an axis of symmetry with respect to the magnetic field.

   
   
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   Fig. 3.

   Magnetic field as a function of latitude along the central meridian (black) compared with that along profiles to the west (green) and east (red) of the two proposed faults. The west curve has been shifted toward the south by 4°, and the east curve has been translated northward by 1° and rescaled as indicated along the horizontal axis. The dashed portion of the west curve indicates the latitude range over which the magnetic imprint was altered by the impact responsible for the multiring crater Ladon. The easternmost profile was taken along a small circle parallel to and eastward of the fault to avoid crossing the proposed fault.

   
   
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   Fig. 4.

   Magnetic field as a function of latitude along a small circle to the east of the proposed faults (solid line) and replotted after adjustment of the horizontal scale (5%) and reflection about 1°N (dashed line).