Martian Magnetic Source Fields

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.

Ionospheric field

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 which 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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