> What kind of event could cause the loss of a planet's magnetic field? Planetary magnetic fields require a liquid ferrous mantle or core. As Mars cooled, its

> What kind of event could cause the loss of a planet's magnetic field? Planetary magnetic fields require a liquid ferrous mantle or core. As Mars cooled, its liquid ferrous material solidified, after which its magnetic field disappeared. The same thing will eventually happen here, and the reason our field still exists is because Earth is a larger planet than Mars, requiring more time to cool down. More details here: http://arachnoid.com/restoring_mars http://arachnoid.com/restoring_mars