A study conducted by the University of Côte d’Azur and the Institute of Celestial Mechanics and Astronomical Calculations (IMCCE) in France has been published in the scientific journal Nature.
Scientists assert that the Moon has a liquid outer core and a solid inner core made of iron, similar to Earth’s core.
Internal structure of Earth’s Moon – (Graphic: Geoazur/Nicolas Sarter).
According to Live Science, astronomers have long been puzzled by the structure of the Moon. A heated debate in the early 20th century revolved around whether it was a primitive rocky world like the moons Phobos or Deimos of Mars.
However, since the first landers touched down on this celestial body, such as NASA’s Apollo missions, hints have emerged that the Moon may be quite similar to Earth in terms of structure.
It is layered much more distinctly than the moons of other planets, not being a homogeneous rock throughout, as revealed by seismic measurement devices. Even the fact that the Moon still experiences light earthquakes suggests this.
The new study utilized a detailed computer model built on geological data from the Apollo program and NASA’s GRAIL mission, a pair of probes that monitored the Moon’s gravitational field for over a year.
The model indicated an inner core with a diameter of about 500 km, corresponding to 15% of the diameter of the entire celestial body.
This research also marked the first time evidence of material disturbance in the Moon’s mantle was found, a process where hotter molten material rises through the mantle, which could explain the presence of iron on the surface of this celestial body.
The Moon’s Remarkable Structure
Examining the internal composition of celestial objects in the Solar System is best achieved through seismic data. This is because seismic waves (essentially sound waves) propagate differently through different materials.
Thus, these waves generated by earthquakes move through a planet (or moon), and their intensity will depend on what they pass through. Currently, scientists have seismic data from the Moon from the Apollo missions, but their resolution is still not high enough to determine the state of the core.
Researchers believe the Moon once had a very strong magnetic field, about 100 times greater than Earth’s, but began to decline around 3.2 billion years ago.
To decode the internal structure of the Moon, a group of French researchers collected data from space missions and laser range experiments on the Moon, creating a profile of the Moon’s characteristics, including its density and the variation in distance from Earth. They then modeled various types of cores to find the one that best fit the observational data.
This allowed the team to make several discoveries. First, they found that material becomes denser as it moves towards the center of the Moon, while less dense material is pushed upwards. This had previously been proposed by researchers as an explanation for the presence of certain elements in the Moon’s volcanic regions. But that is only part of the overall picture of the Moon’s true structure.
According to the model created based on data from the Apollo missions, the Moon’s core consists of an outer liquid layer and a solid inner core. There, the outer core has a radius of about 362 km, and the inner core has a radius of about 258 km.
The researchers also discovered that the Moon’s core is very similar to Earth’s core, with an outer liquid layer and a solid inner core. The core has a diameter of about 500 km, equivalent to 15% of the Moon’s width. Coincidentally, in 2011, a team led by NASA experts found nearly identical results using seismic techniques on Apollo data to study the Moon’s core.
Although this discovery provides certain insights into the structure of the Moon, many other mysteries about this natural satellite remain unsolved, such as what happened to its magnetic field. Shortly after its formation, the Moon had a very strong magnetic field, but this began to decline around 3.2 billion years ago.
The study also found evidence of another intriguing phenomenon known as “layer inversion”, occurring on the Moon. Simply put, this is the idea that material from the mantle, the intermediate layer, and the outer core of the Moon is quite disturbed.
In the future, we may have more data about the Moon for research, as government agencies and private space companies are conducting their new lunar missions. NASA hopes to send four astronauts on the Artemis II mission in 2024 to fly close to the Moon, while companies like ispace, Astrobotic, and Intuitive Machines also have their own plans.
