Total magnetic field strength at the surface of the Moon as derived from the Lunar Prospector electron reflectometer experiment.
The external magnetic field of the Moon is very weak in comparison to the Earth. Other major differences are that the Moon does not currently have a dipolar magnetic field (as would be generated by a geodynamo in its core), and the magnetizations that are present are almost entirely crustal in origin. One hypothesis holds that the crustal magnetizations were acquired early in lunar history when a geodynamo was still operating. The small size of the lunar core, however, is a potential obstacle to this theory. Alternatively, it is possible that on an airless body such as the Moon, transient magnetic fields could be generated during large impact events. In support of this, it has been noted that the largest crustal magnetizations appear to be located near the antipodes of the giant impact basins. It has been proposed that such a phenomenon could result from the free expansion of an impact generated plasma cloud around the Moon in the presence of an ambient magnetic field.[1] Image File history File links Moon_LP_ER_magnetic_field. ... Image File history File links Moon_LP_ER_magnetic_field. ... Apparent magnitude: up to -12. ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ... This world map (in red) is overlaid with an antipodal map (in yellow) showing the antipodes of each point on the Earths surface. ...
Radial gravitational anomaly at the surface of the Moon. ...
References
^ Hood, L. L., and Z. Huang (1991). "Formation of magnetic anomalies antipodal to lunar impact basins: Two-dimensional model calculations". J. Geophys. Res.96: 9837-9846.
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