Scientists finally have an answer for a long-standing question: what is inside the moon?

Scientists have finally answered one of the Moon's biggest mysteries: its inner core. A detailed study conducted in May 2023 confirmed that the Moon's inner core is a solid sphere with a density similar to that of iron. The revelation is a pivotal breakthrough in understanding the Moon’s internal structure and its evolution.

For years, experts debated whether the Moon's core was solid or molten, but recent studies have settled the question, confirming the inner core's solid state. The researchers used seismic data to study the Moon's interior composition. The team, led by astronomer Arthur Briaud from the French National Centre for Scientific Research, obtained seismic data from several space missions and laser-ranging experiments on the Moon to determine its inner core state.

Briaud and his team compared the lunar seismic data with different kinds of cores to find the closest match. They used this data to study the Moon's characteristics, such as its gravitational relationship with Earth and its density. 

The research revealed that the Moon has an internal structure divided into layers, similar to Earth. The Moon has an outer fluid layer and a solid inner core, similar to Earth. The solid inner core of the Moon has a radius of about 258 kilometers (160 miles), and the outer core has a radius of about 362 kilometers (225 miles). The inner core has a density of about 7,822 kilograms per cubic meter, indicating a high presence of iron.

One of the most significant aspects that emerged from the research is the presence of overturn activity in the lunar mantle. In the lunar mantle, denser material is moving toward the center, while less dense material is rising toward the surface. This phenomenon could explain the presence of certain elements in the volcanic regions of the Moon.

The findings by Briaud's team are a confirmation of earlier research by Renee Weber's team from NASA's Marshall Space Flight Center in 2011, which also used state-of-the-art seismic techniques on Apollo data. The 2011 study found evidence of a solid inner core on the Moon with a radius of about 240 kilometers and a density of approximately 8,000 kilograms per cubic meter.

The composition of the lunar core is crucial for understanding how and why the Moon's magnetic field disappeared over time. The Moon's magnetic field began to decline about 3.2 billion years ago, which is key to understanding its formation and evolution. A magnetic field is generated by motion and convection in a planet or moon's core.

The findings were reported by Science Times, and Science Alert, among other websites. 

This article was written in collaboration with generative AI company Alchemiq