Well, the verdict already exists. After all, the moon is not made of green cheese.
A thorough investigation published in May 2023 found that the core of the moon is actually a solid sphere of density similar to iron. The researchers hope this will help solve the long debate about whether the moon's heart is solid or melted, and give people a more accurate understanding of the moon's history and the history of the solar system.
“Our results question the evolution of the lunar magnetic field, thanks to its presence at the internal core and support for global mantle coverage scenarios, bringing Solar System System System's first bill bombing timeline, which brings substantial insights,” wrote a team led by astronomer Arthur Briaud of the French National Centre for Scientific Research.
Watch the following video for a summary of what they found:
YouTube thumbnails
Through seismic data, it is most effective to most effectively detect the internal composition of objects in the solar system. The way sound waves produced by earthquakes move and reflect from inside a planet or the moon can help scientists create detailed maps of the interior of objects.
We happen to have the moon seismic data collected by the Apollo mission, but the resolution is too low to accurately determine the state of the kernel. We know there is an external core of the fluid, but what it contains is still being debated. Models of solid and fully fluid cores are just as good as Apollo data.
For a once-for-all, Briaud and his colleagues gathered data from space missions and lunar laser range experiments to compile the outlines of various lunar features. These include its interaction with the gravity of the Earth, its change in distance with the Earth, and its degree of change in density.
The artist’s impression of different instruments to measure the characteristics of the moon to reveal its core. (géoazur/Nicolas Sarter)
Next, they model using various core types to find the one that best matches the observed data.
They made some interesting discoveries. First, most similar to the model we know about the moon describes the activity deep inside the moon.
This means that the denser material inside the moon falls in the center, and the less dense material rises. This activity has long been proposed as a way to explain the existence of certain elements in the lunar volcanic region. The team's research adds another point to the evidence “for”.
They found that the moon's core is very similar to the core of the Earth – the outer fluid layer and the solid core. According to their modeling, the radius of the outer core is about 362 kilometers (225 miles) and the radius of the inner core is about 258 kilometers (160 miles). It is about 15% of the entire radius of the moon.
The team found that the density of the kernel was also about 7,822 kilograms per cubic meter. This is very close to the density of iron.
Strangely, in 2011, a team led by NASA Marshall planetary scientist Renee Weber used what was then the most advanced seismic technology on Apollo data to study the core of the moon. They found evidence of a solid core with a radius of about 240 kilometers and a density of about 8,000 kilograms per cubic meter.
Briaud and his team said their results confirm these early discoveries, which constitute a very powerful case for the Earth-Linar Core. This has some interesting implications for the evolution of the moon.
We know that shortly after its formation, the moon had a strong magnetic field that began to decline about 3.2 billion years ago. Such a magnetic field is generated by motion and convection in the core, so the formation of the moon core is very relevant to how and why the magnetic field disappears.
Given that humans hope to return to the moon in a relatively short time, perhaps we won’t wait for the earthquake verification of these discoveries for a long time.
The study has been published in nature.
A version of this article was first released in May 2023.
