What drove the lunar dynamo?
New evidence from an ancient lunar rock suggests that the moon once harbored a long-lived dynamo — a molten, convecting core of liquid metal that generated a strong magnetic field 3.7 billion years ago. The findings, published today in Science, point to a dynamo that lasted much longer than scientists previously thought, and suggest that an alternative energy source may have powered the dynamo. “The moon has this protracted history that’s surprising,” says co-author Benjamin Weiss, an associate professor of planetary science at MIT. “This provides evidence of a fundamentally new way of making a magnetic field in a planet a new power source.” The new paper is the latest piece in a puzzle that planetary scientists have been working out for decades. In 1969, the Apollo 11 mission brought the first lunar rocks back to Earth — souvenirs from Neil Armstrong and Buzz Aldrin’s historic moonwalk. Since then, scientists...