Some Metal Meteorites Have a Tiny Magnetic Field. But How?

A portion of the metallic meteorites found on Earth have traces of magnetism. This is surprising since you need a larger world with an internal dynamo like the Earth. New research suggests that iron-heavy asteroids can collect into piles of rubble, with other space rocks forming a cold inner pile surrounded by a warmer liquid outer layer. As the core draws heat from the outer layer, it initiates convection and a small magnetic field that is detectable in the iron meteorites billions of years lat...