MGS data from 1997 through 2006 have revealed very strong remnant crustal fields on Mars. These crustal fields are much stronger, possibly up to 10 times as strong, than the crustal fields found here on Earth. So far the fields have only been observed from the MGS mapping altitude of 400 km, with a few swoops down to 100 km during the initial orbit insertion phase.

The presence of crustal fields implies that Mars may have had an active internal dynamo, perhaps similar to that of Earth, earlier in its life-story.

The crustal fields observed on Mars are mainly located in the southern hemisphere where the Martian landscape is more topologically interesting and presumably older. The topology of the area, however, makes it a difficult landing site for current Mars lander missions.

The presence of these crustal fields causes local mini-magnetospheres that reach up to more than 1500 km above the Martian surface. These mini-magnetospheres are therefore high enough to disturb the boundaries of the induced global magnetosphere of Mars; mainly the MPB (Magnetic Pileup Boundary) is affected by this.



The mini-magnetospheres also affect the plasma sheet stretching out behind Mars, pushing it away from the surface above areas with strong crustal fields, as described by Halekas et al. 2006.

Knowing the field in 400 km altitude, however, does not tell us much about the actual sources of the measured field. Closer down towards the surface we know very little about the size and extent of the physical field, even though several models on different scenarios of sources to accommodate the MGS data has been constructed.

In order to understand the magnetic field of Mars we now need to make measurements closer to the surface, and to accommodate this need scientists at DTU Space have developed a magnetometer that is to be part of the next European Mars lander mission, ExoMars.