Earth’s magnetic field may be result of impact with Mercury-like body

Los Angeles Times : The general theory for the formation of Earth is that it is a conglomeration of rocky objects like those currently in the asteroid belt. By itself, that theory doesn’t explain why there are enough radioactive elements in Earth’s core to provide the energy for driving the planet’s magnetic field. Those elements like to bond with oxides, and the combined molecules would be light enough to move out of Earth’s core. Now, Bernard Wood and Anke Wohlers of the University of Oxford in the UK propose an answer. They modeled a high-pressure environment where radioactive elements were mixed with oxygen-lacking sulfur compounds. The radioactive elements strongly bonded with the sulfur-rich metals and created compounds heavy enough to stay in the core. However, Earth is rich in oxides and poor in sulfides. To have had enough sulfides to establish a magnetic field, early Earth would have to have been impacted by a body rich in sulfides, much like Mercury, but with the mass of Mars. That same impact may have also given birth to the Moon.