Moon Had Molten Core

Scientists asserted that the Moon rocks returned by the Apollo astronauts would keep researchers busy for decades. An analysis on one of the rocks collected during the Apollo 17 mission has helped to solve a longstanding enigma about the Moon. Researchers at the Massachusetts Institute of Technology (MIT) carried out the most detailed analysis ever of the oldest pristine rock from the Apollo collection. Magnetic traces recorded in the rock provide strong evidence that 4.2 billion years ago the moon had a liquid core with a dynamo, like Earth's core today, that produced a strong magnetic field.

Ben Weiss, Assistant Professor of Planetary Sciences in MIT's Department of Earth, Atmospheric and Planetary Sciences said: “Until the Apollo missions, many scientists were convinced the moon was born cold and stayed cold, never melting enough to form a liquid core. Apollo proved that there had been massive flows of lava on the moon's surface, but the idea that it has, or ever had, a molten core remained controversial. "People have been vociferously debating this for 30 years,"

Many of the rocks returned from the Moon had magnetic qualities, which was perplexing to scientists. How could Moon rocks be magnetic if the Moon had no magnetic core?
One rock in particular was compelling. The rock was collected on Apollo 17, the last Apollo mission to the moon, by Harrison "Jack" Schmidt, the only geologist ever to walk on the moon. "Many people think that it's the most interesting lunar rock.

The magnetic field necessary to have magnetized this rock would have been about one-fiftieth as strong as Earth's is today. This is consistent with dynamo theory," and also fits in with the prevailing theory that the moon was born when a Mars-sized body crashed into the Earth and blasted much of its crust into space, where it clumped together to form the moon.