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CAPTION: A map of the vertical (radial) component of magnetic fields originating from the Martian crust, obtained by the magnetometer aboard Mars Global Surveyor, overlaying a photo of the Martian surface. The north pole is at the top. Note the band structure in the southern hemisphere around 180 degrees longitude, with alternating polarities as you move from south to north.
Only about 20% of the surface has been mapped at this resolution. Blue hues represent fields directed radially into the surface, while red hues show outward directed fields, approaching 1500 nanoTeslas at the spacecraft altitude of about 110 kilometers. For comparison, the magnetic field at the Earth‚s surface is about 30,000 nanoTeslas, or a third of a Gauss. The dark line snaking through the center of the photo is the dichotomy boundary, separating the two hemispheres of Mars. (Credit: Adapted from Acuna et al., Science 284, 790, 1999.)
print-quality image: 72dpi, 448K
CAPTION: A map of the ionosphere on Mars, or more specifically, the probability that Mars Global Surveyor will be in the ionosphere when orbiting at 400 kilometer's altitude. Blue is a low probability, meaning the spacecraft is usually in the solar wind and the ionosphere is below the spacecraft. Yellow and red show where the ionosphere often protrudes above 400 km altitude. The yellow and red areas where the ionosphere extends to higher altitudes correspond with areas of strong magnetic field on the surface. (Credit: David Mitchell, UC Berkeley.)