Young asteroids generated long-lasting magnetism
Meteorites chronicle conditions on cooling space rocks
Ancient meteorites reveal that young asteroids may have generated powerful magnetic fields for hundreds of millions of years longer than once thought. The finding could explain long-lasting magnetism elsewhere in the early solar system, such as on the young moon (SN Online: 12/4/14).
Planetary scientist James Bryson of the University of Cambridge and colleagues examined two South American meteorites left over from asteroids roughly 400 kilometers wide (about a ninth of the moon’s diameter). Tiny pockets of iron and nickel embedded in the space rocks aligned with their parent asteroid’s magnetic field as they formed billions of years ago, providing a datable snapshot of the asteroids’ magnetism. Inspecting the iron and nickel using X-rays, the team discovered that each asteroid produced a strong magnetic field for well more than 100 million years.