Moon’s inner core consist of what?

 The Moon has a solid iron core, Scientists have found the answer!

Scientists have finally confirmed what lies at the heart of the moon, and the discovery is more familiar than we expected. It is now confirmed that the Moon has a solid inner core with a density similar to iron. The core's structure mirrors that of Earth's, with a fluid outer layer and solid inner core, which has substantial implications for understanding Moon's history and the evolution of the Solar System. This is a major scientific breakthrough which has settled a decades-old debate about the moon’s interior. Researchers have confirmed that the moon has a solid inner core, similar to Earth’s, composed of iron with a density of about 7,822 kg/m³. This discovery not only changes how we understand the moon’s structure but also provides new insights into the history of our solar system.

For years, scientists have debated whether the moon’s core was fully molten or partially solid. Previous studies offered conflicting results, largely due to the limitations of Apollo-era seismic data. While researchers knew the moon had a fluid outer core, the question of whether a solid core existed remained unanswered. A new study published in Nature has found that the Moon has a solid inner core with a density similar to that of iron. A research team led by astronomer Arthur Briaud from the French National Centre for Scientific Research explored what’s inside the Moon. They used data from space missions and lunar laser-ranging experiments to develop models that best fit the Moon’s known characteristics. They combined data from space missions, lunar laser-ranging experiments, and gravitational analyses to build an updated model of the moon’s interior. Their findings have finally given crucial insights into the Moon’s history and, by extension, the evolution of the Solar System. Their findings also confirmed that the moon’s core structure mirrors Earth’s, with a solid inner core surrounded by a molten outer layer. "Our results question the evolution of the Moon's magnetic field thanks to its demonstration of the existence of the inner core and support a global mantle overturn scenario that brings substantial insights on the timeline of the lunar bombardment in the first billion years of the Solar System,” astronomer Arthur Briaud of the French National Centre for Scientific Research in France wrote in the study. The study estimates that the moon’s inner core has a radius of 258 km's (160 miles), making up about 15% of the moon’s total radius. It is surrounded by a fluid outer core that extends to 362 km's (225 miles). This layered structure closely resembles the Earth’s inner and outer core. As per their calculations, the inner core’s density is estimated at 7,822 kilograms per cubic meter, which is very close to that of iron.

Seismic data is the most effective way to understand the interiors of celestial bodies. Though Apollo mission seismic data uncovered the presence of a fluid outer core, it failed to determine whether the inner core was solid or molten. In order to understand it, Briaud’s team analysed data on the Moon’s gravitational deformation, distance variations from Earth and density. These models further confirmed that the Moon's structure closely resembles Earth’s core, with an outer fluid layer and a solid inner core. Interestingly, this new research reinforces findings from a 2011 NASA study that also suggested the presence of a solid core, although with slightly different measurements. However, Briaud’s team has now provided stronger evidence, using more advanced computer modelling and updated observational data. Briaud’s new research has underlined the case for an Earth-like lunar core. A planet’s magnetic field is generated by movement within its core, where molten metal flows and creates an electric current. Understanding the composition and behaviour of the moon’s inner layers helps explain how and why its magnetic activity faded over time. One of the most fascinating implications of this discovery is how it relates to the moon’s ancient magnetic field. Scientists believe the moon once had a strong magnetic field, similar to Earth’s, but it started to decline about 3.2 billion years ago. As magnetic fields are generated by core convection, understanding the Moon’s core composition may explain why its field disappeared. The study also supports the theory of “mantle overturn”, a process where denser materials sink toward the core while lighter elements rise toward the surface. This could explain why certain elements are found in the moon’s volcanic regions, adding another piece to the puzzle of lunar evolution. 

Future missions could provide even more detailed measurements of the moon’s internal structure, helping refine our understanding of its formation and geological history. With every new discovery, scientists uncover more about the moon’s complexity and evolution. NASA’s Artemis program, which aims to return astronauts to the moon, presents a valuable opportunity to test these findings with more advanced seismometers.