Unlike Earth, the moon no longer has a core-generated magnetic field. On our planet, the movement of liquid iron in the outer core generates a global magnetic field. This so-called geodynamo works on a similar principle to a bicycle dynamo, which converts mechanical motion into electrical energy. "T oday, there is an ongoing heated debate as to whether the moon also operated a dynamo in the past," says Xi Yang, a Ph.D. student in the Department of Earth and Planetary Sciences at ETH Zurich. This is because analyses of rock samples brought back to Earth by the Apollo astronauts are contradictory. ...read more read less