Research on an ancient lunar rock suggests that almost 4 billion years ago, the moon once had a molten, core of liquid metal that generated a strong magnetic field.
The Daily Galaxy quotes planetary scientist Benjamin Weiss as saying, "The moon has this protracted history that’s surprising."
In 1969, the Apollo 11 mission brought the first lunar rocks back to Earth as souvenirs from Neil Armstrong and Buzz Aldrin’s historic moonwalk. Since then, scientists have studied them for clues to the moon’s history. They soon discovered that many rocks were magnetized, which suggested that the moon may have harbored a convecting metallic core that produced a large magnetic field, now recorded in the moon’s rocks.