Boston (MA) - Researchers at MIT say they've found the answer to the question of why the lunar rocks brought back by Apollo astronauts from the moon produce magnetization. It has to do with the notion that the moon once had a liquid core which acted as a dynamo, like Earth today, which produced a strong magnetic field.
MIT staff carried out a thorough analysis of the oldest pristine rock from the Apollo collection. The team used a commercial rock magnetometer that was specially fitted with an automated robotic system to take readings. Faint magnetic traces in this rock provided them knowledge that over 4 billion years ago the moon's core was much more active.
The magnetic field necessary to have magnetized this rock would have been about one-fiftieth as strong as the Earth's is today, the researchers said. The more sophisticated equipment allowed them to study the magnetization of the rock in much greater detail than was previously possible. The data they collected also let them rule out other possible magnetic sources, such as magnetic fields briefly generated by some of the huge impacts on the moon.
This particular rock was of great value to the study as it is the oldest of the rocks in inventory to not have been subject to impact shocks on the moon – as such impacts erase all evidence of earlier magnetic fields.