3 Questions: Rona Oran and Benjamin Weiss on the ancient moon's missing magnetism

MIT: 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 ...