Magnetic fields measured near Mars reveal that it has no internal magnetic field of global scale at the present time (Purucker et al.2000).
Crustal magnetic anomalies have been recently discovered by Mars Global Surveyor (MGS) near the martian surface.
Recently Mars Global Surveyor
(MGS) performed the magnetic survey near the martian surface
The maximum magnetic field measured by MGS at the altitude of is
20 times larger than that measured by Earth
orbiting satellites at a comparable altitude. Previous studies of
magnetic fields measured near Mars showed that
Mars does not posess internal magnetic field of global scale at
the present time. Therefore in the absence of core
field martian crustal anomalies are due to remanent magnetic component.
One can see that the the strongest magnetic
anomalies are related to Terra Cimmeria and Sirenum in the heavily
cratered uplands of Mars' southern hemisphere.
Modeling of magnetic profile data from this area (Connerney
et al., 1999) by Connerney and his colleagues suggest
magnetization value about 20 A/m and crustal thickness about 30
km. On the Earth only fresh mid-oceanic basalts
hold coherent magnetization (which extend for 2000km as the martian
magnetic sources do) about 20 A/m.
However these basalts are thin (layer no more
than 1 km.) and magnetic signal which they create at the satellite altitude
is small. Modeling of the shape and the amplitude of
Kursk satellite magnetic anomaly (one of the largest
on the Earth)
suggest that it's source reside deep in the crust
(Taylor et al., 2000). However we know little about the deeper sources
contributes substantially to the magnetic anomalies at satellite
altitude. Connerney and colleagues argue that the long linear Martian sources
may be the signature of a plate tectonics or crustal recycling process.
The nature of this process is hotly debated.
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Last modified on May 15, 2001