Massachusetts Institute of Technology
Today, the moon lacks a global magnetic field, but this wasn’t always the case. Spacecraft measurements of the moon’s crust and lunar rocks retrieved by the Apollo missions contain remnant magnetization that formed 4 to 3.5 billion years ago in a magnetic field comparable in strength to that of the Earth. Scientists have argued that the source of this was a dynamo – a magnetic field generated by the moon’s churning, molten, metal core. However, research indicates that the moon’s suspected small core may not have been able to generate enough energy to sustain the ancient magnetic field that planetary scientists have inferred from in its rocks.