Unlike Earth, the moon does not have a global magnetic field, at least not today.
But scientists theorized that the moon, despite being only 1 percent the mass of Earth, had a moving, molten metallic core, which could generate a global magnetic field.
Other researchers are not so sure. They suspect the lunar soil picked up magnetic fields from impacting asteroids and other bodies, which spawned short-lived, but repeated, electrically charged plasmas.
A new study provides evidence that the moon not only had a magnetic heart, but that it initially beat stronger than Earth’s churning core does today.
“We see this super strong field and then it just drops off a cliff. Everywhere points to this large-scale geophysical process,” planetary scientist Benjamin Weiss, with the Massachusetts Institute of Technology, told Discovery News.
The study, based on a reanalysis of the Apollo samples, combined with data collected by a host of orbiting robotic probes, raises questions about how electrical conducting fluids came to exist in the moon’s core, creating a so-called dynamo that generated a global magnetic field.
Weiss and colleagues also are curious about why the field had such a dramatic demise.
Their analysis shows that the moon had a dynamo-driven magnetic field 4.2 billion to 3.6 billion years ago.
“The record of past magnetic fields are recorded in rock, the microscopic alignment of electrons in the rock, like little compass needles,” Weiss said. “The more of them that are aligned, the stronger the magnetic field.”
Additional analysis to look at the direction of the electrons’ alignment could help scientists figure out if the dynamo was stirred up by changes in the moon’s spin angle, or if other factors were responsible.
“Maybe every time the moon was hit by a big impact it underwent this major rotation, the north pole became a different location,” Weiss said.
“You can test that idea by measuring magnetization direction as a function of time,” he added.
Read more at Discovery News
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