Planetary Science

Martian Magnetism

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Science  16 Nov 2001:
Vol. 294, Issue 5546, pp. 1421
DOI: 10.1126/science.294.5546.1421a

The magnetometer experiment onboard the Mars Global Surveyor spacecraft has been mapping the magnetic field intensity of the Martian crust for several years in order to understand the physical and chemical evolution of Mars.

Connerney et al. have completed a detailed global map of magnetic intensity in the crust. Relatively high magnetic intensities of normal and reverse polarity form linear features only in the southern hemisphere where the crust is the oldest. These features indicate that Mars had an active dynamo that reversed its the magnetic field in the ancient past. More recently, the dynamo stopped, and so the younger crust shows no remnant magnetic signature. In addition, the oxidation state that would have been necessary to crystallize the appropriate magnetic iron oxides suggested by the magnetic signatures requires that the mantle-derived magmas interacted with an aqueous component. This provides more evidence for an early Martian environment that was more active and wetter than today.—LR

Geophys. Res. Lett.28, 4015 (2001).

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