Well, the verdict has been rendered. The moon is not made of Green cheese After all that.
A comprehensive investigation published in May found that the moon’s inner core is actually a solid sphere with a density similar to that of iron. Researchers hope this will help settle a long-standing debate about whether the moon’s inner core exists or not solid or moltenIt leads to a more accurate understanding of the history of the Moon, and thus the history of the solar system.
“Our results” Written by a team led by astronomer Arthur Briaud From the French National Center for Scientific Research in France, “questions the evolution of the Moon’s magnetic field thanks to the proof of the existence of the inner core and supports a global mantle inversion scenario that provides fundamental insights into the timeline of lunar bombardment in the first billion years of the solar system.”
The internal structure of objects in the solar system is most effectively investigated through seismic data. The way sound waves from earthquakes move through and reflect off material inside a planet or moon can help scientists create a detailed map of the body’s interior.
We have lunar seismic data collected by the Apollo mission, but the resolution of this data is too low to accurately determine the state of the inner core. We know that there is a liquid outer coreBut what it includes is still under discussion. The solid inner core and completely liquid core models work well with the Apollo data.
To find out once and for all, Briaud and his colleagues collected data from space missions and… Lunar laser range Experiments to gather insight into different lunar features. These include the degree to which it is distorted due to gravitational interaction with the Earth, the difference in its distance from the Earth, and its density.
They then ran modeling using different base types to find the one that best matched the observational data.
They have come to many interesting results. First, models that closely resemble what we know about the Moon describe active overturning deep in the Moon’s mantle. This means that the denser material inside the moon falls toward the center, and the less dense material rises to the top. This activity has long been proposed as a way to explain The presence of certain elements In volcanic regions of the moon. The team’s research adds another point to the “for” list of evidence.
They found that the Moon’s core is very similar to Earth’s core, with a liquid outer layer and a solid inner core. According to their model, 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). This represents about 15 percent of the radius of the entire Moon.
The team also found that the density of the inner core is about 7,822 kilograms per cubic meter. This is very close to Iron density.
Interestingly, in 2011, a team led by NASA Marshall planetary scientist Rene Weber reached a similar conclusion using what were then state-of-the-art seismic techniques based on Apollo data to study the moon’s core. They found evidence It is a solid inner core with a radius of about 240 kilometers, and a density of about 8,000 kilograms per cubic meter.
Briaud and his team say that their findings confirm those previous findings, and constitute a very strong argument for the existence of an Earth-like lunar 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, which began to decline about 3.2 billion years ago. Such a magnetic field is created by motion and convection in the core, so what the moon’s core is made of is closely related to how and why the magnetic field disappears.
Given humanity’s hope of returning to the Moon in a relatively short time, we may not have long to wait for seismic verification of these results.
The research was published in nature.
A version of this article was first published in May 2023.