Details On The Demise Of The Moon's Magnetic Field Announced

If we took a compass to the moon today, it wouldn't work because the moon has no magnetic field. That wasn't always the case. Scientists at MIT have pinned down the timing of the demise of the lunar dynamo. Scientists say that at one point in the lifecycle of the moon, billions of years ago, it had a magnetic field that was likely stronger than the field that the Earth has today.

At some point in the lifecycle of the moon, the magnetic field, and the lunar dynamo that created it died off. MIT scientists have pinned down the timing of the demise of the lunar dynamo to about 1 billion years ago. The discovery also favors one theory on what drove the lunar dynamo in its later stages. That theory is core crystallization.

Scientists say that as the core crystallized, the liquid core's electrically charged fluid was buoyantly stirred to produce the dynamo. The team says that they discovered the magnetic field on the moon ended somewhere between 1 and 1.5 billion years ago and that it was powered in an Earth-like way.

The team says that by figuring out when the magnetic field ended, you could figure out what causes the lunar dynamo because all the theories on how it was generated had different lifetimes. The team looked at lunar rock samples collected by astronauts in the Apollo era. Rocks that spewed out early in the moon's lifecycle had microscopic grains aligned to the moon's magnetic field, preserving a record of that field.

The team says that the past 3 billion years of lunar history is a mystery because there is little rock record of it. Scientists believe that about a billion years ago, there was a massive impact with the moon that melted rock and welded it back in a what that much of the ancient magnetic record was lost. Rocks after the impact have random orientation suggesting no magnetic field. Radiometric dating of the rocks gave an idea of when the magnetic field ended.