A comprehensive investigation published in May 2023 revealed that the Moon's inner core is, in fact, a "solid ball" with a density similar to that of iron.
This, the researchers hope, will help resolve a long-standing debate over whether the Moon's core is solid or molten, and lead to a more accurate understanding of the history of our satellite – and by extension, that of the Solar System.
"Our results," wrote a team led by astronomer Arthur Briaud of the French National Center for Scientific Research, "call into question the evolution of the Moon's magnetic field thanks to the demonstration of the existence of its inner core."
It is known that the investigation of the internal composition of objects in the Solar System is carried out more effectively through seismic data.
The way acoustic waves created by earthquakes move and reflect off material inside a planet or moon can help scientists create a detailed map of the object's interior.
There is lunar seismic data collected by the Apollo missions, but its resolution is too low to accurately determine the state of the inner core.
A liquid outer core is known to exist, but what comprises the core is unknown, writes science alert, the Telegraph reports.
To figure it out once and for all, Briaud and his colleagues gathered data from space missions and lunar laser beam experiments to compile a profile of various lunar features.
These include the rate of its deformation by gravitational interaction with the Earth, the change in its distance from the Earth, and the density.
Next, they ran simulations with different nuclear types to find which best matched the observational data.
As reported, they made some interesting findings.
First, the models that most resembled what we know about the Moon described active inversion deep within the lunar mantle.
This means that the denser material inside the Moon falls towards the center and the less dense material rises up.
This activity has long been proposed as a way to explain the presence of certain elements in the Moon's volcanic regions.
The team's research adds another point to the "for" list of evidence.
And they found that the lunar core is very similar to Earth's - with a liquid outer layer and a solid inner core.
According to their modeling, the outer core has a radius of about 362 kilometers and the inner core has a radius of about 258 kilometers.
The inner core, the team found, also has a density of about 7,822 kilograms per cubic meter.
Surprisingly, in 2011, a team led by NASA Marshall planetary scientist Renee Weber found a similar result using the latest seismological techniques on Apollo data to study the lunar core.
They found evidence of a solid inner core with a radius of about 240 kilometers and a density of about 8,000 kilograms per cubic meter.
Their results, Briaud and his team say, are confirmation of those earlier findings. And this has some interesting implications for the evolution of the Moon.
We know that not long after it formed, the Moon had a strong magnetic field, which began to disappear about 3.2 billion years ago.
Such a magnetic field is created by motion and convection in the core, so what the lunar core is made of is deeply relevant to how and why the magnetic field disappeared. /Telegraph/
