Scientists have made a groundbreaking discovery after more than 50 years of study: the moon has a solid inner core just like the Earth. The moon’s interior structure has long been a mystery, and astronomers have been debating whether the moon is a primitive rocky world or whether it has a rich inner geology. The first indication that the moon had an Earth-like interior came from NASA’s Apollo missions. Data from lunar landers’ instruments suggested that the celestial body was differentiated, meaning that it was layered with denser material at the center and less dense material closer to the surface.
In 2011, NASA research suggested that the moon’s outer core was made of fluid iron, and there was a partially melted layer where it met the mantle. The study also indicated the possibility of an iron-based inner core. However, it wasn’t until a recent study from a team of researchers from the Côte d’Azur University and the Institute of Celestial Mechanics and Ephemeris Calculations (IMCCE) in France that the existence of the moon’s inner core was confirmed.
The researchers utilized a detailed computer model based on geological data from the Apollo program and NASA’s GRAIL mission to create a clearer picture of the moon’s insides. The study determined that the moon’s inner core is approximately 310 miles (500 km) in diameter, making up only 15% of the moon’s width. This small size explains why it has been so difficult for scientists to detect it.
The study also uncovered the first evidence of mantle overturn on the moon, a process by which warmer molten material rises through the mantle. The researchers suggested that this process may explain the presence of iron on the moon’s surface.
The discovery of the moon’s solid inner core has significant implications for our understanding of the moon’s geologic mysteries, including the once-powerful lunar magnetic field that samples suggest rivaled Earth’s. As governmental agencies and private space companies prepare for new lunar missions in the coming decade, the promise of more data is right around the corner. The new information will enable us to gain a deeper understanding of the moon’s inner workings and perhaps uncover new insights into the history of our solar system.