Earth’s only satellite holds many secrets. Just this year, scientists discovered caves on the Moon formed by lava tubes, which were formed by basaltic lava flows. The Moon’s inner core has raised even more questions in recent years – is it solid or molten? This ongoing debate has fueled extensive research around the world. That’s because understanding the composition of the Moon’s core provides vital insights into the formation and evolution of not only Earth’s satellite, but also other celestial bodies in the Solar System. Fortunately, all the i’s have finally been dotted – a study published in the journal Nature has shown that the Moon’s inner core is indeed solid, with a density close to that of iron. This breakthrough discovery could revolutionize our understanding of the Moon’s evolution and its magnetic field.
Well, now it all falls into place – the Moon isn't made of cheese. Image: cff2.earth.com
Contents
- 1 What is the Moon made of?
- 2 The Lunar Core
- 3 Exploring the Lunar Interior
- 4 Why is this important?
What is the Moon made of?
As children, many of us believed that the Moon was made of cheese. As adults, we realized that this was just a silly joke – like all celestial bodies in the solar system, rock is a more realistic ingredient. However, because the satellite can be observed with the naked eye directly from Earth, people throughout human history have been intrigued by the dark and light spots on its surface.
Today we know that the lunar surface is covered with extinct volcanoes, impact craters and lava flows, but in the past scientists seriously believed that the dark areas of the Moon could be covered with oceans and called them mare, which is Latin for “seas” (maria when there is more than one). As it turns out, mare are indeed oceans of sorts, only instead of water they consist of pools of solidified lava. There is also plenty of evidence of asteroids on the Moon's surface, which are easy to see with a telescope.
This photo was taken by Apollo 17 in 1972. To the left of center is the crater Pytheas. Closer to the top is the crater Copernicus. Image: cdn.mos.cms.futurecdn.net
Like Earth, the Moon has a crust, mantle, and core. The rocky surface of our satellite, for example, is covered with regolith. When asteroids and meteorites collide with the surface, they break it into small pieces, which leave imprints (for example, the famous footprint of Neil Armstrong). The thickness of the lunar crust is from 60 to 100 kilometers, and the depth of the regolith on the surface can reach from 3 to 20 meters.
More on the topic: The Moon also has an atmosphere – now we know where it came from
It should also be noted that the Moon is the second densest satellite in the Solar System, second only to Jupiter's Io. The division of the Moon's interior into layers was probably caused by the crystallization of a magma ocean shortly after its formation. However, the lunar core has always raised the most questions for scientists – what is it like, is it solid or liquid? And how can we find out?
Lunar core
It should be noted that studying the interior of a satellite like the Moon is not an easy task, especially when the available data is not particularly detailed. For this reason, studying the interior composition of Solar System objects is most effectively carried out using seismic data – the way acoustic waves generated by earthquakes pass through and bounce off the material inside a planet or Moon helps to create a detailed map of the interior of a celestial body.
Most of the interior of the Moon consists of lithosphere, which is about 1000 km thick. Image: naked-science.ru
To learn more about the interior structure of the Moon, scientists used seismic data collected during the Apollo mission, but their resolution was too low to accurately determine the state of the inner core. So, it is known that the outer core is fluid, but what exactly it is has remained a mystery all these years.
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Fortunately, everything has changed thanks to scientists from the French National Center for Scientific Research (CNRS), led by astronomer Arthur Briot, who have finally dotted the i's and crossed the t's by combining data from space flights and experiments, the degree of deformation of the Moon as a result of gravitational interaction with the Earth, changes in the distance to the Earth and its density.
Our results call into question the evolution of the Moon's magnetic field by demonstrating the existence of an inner core and support the scenario of a global mantle reversal, which provides significant insight into the timing of the emergence of the lunar magnetic field, the authors of the scientific paper write.
In simple terms, Briot and his team found that the lunar mantle has turned upside downwhen the Moon had just formed. This means that what was on top of our satellite ended up on the bottom, and what was on the bottom ended up on the surface. It turns out that the Moon's inner core is a solid ball with a density close to that of iron.
Exploring the Moon's Interior
In their work, Brio and his team combined existing seismic data with information from space missions and the Lunar Laser Ranging experiment and used them to model the moon's core. The results showed that the moon's mantle, the layer above the core, is actively turning over. This means that denser material is moving toward the center, while less dense material is rising toward the surface.
The ancient Moon generated a magnetic field in its liquid metal core. Image: cdn.sci.news
The key finding of the new study is the striking similarity between the cores of the Moon and Earth: Like our planet, the Moon appears to have a liquid outer layer surrounding a solid inner core. This intriguing similarity leads the researchers to important questions about the formation and evolution of both bodies.
If the Moon's core matches the Earth's core, this indicates that both bodies may have formed as a result of similar geological processes over billions of years, the authors of the scientific paper believe.
The discovery of a solid inner core on the Moon has huge implications for our understanding of the history of its magnetic field. Magnetic fields are typically created by the movement and convection of molten metal in the planet's core, which leads to electric currents. The discovery also challenges long-held assumptions by focusing on the mechanisms underlying the gradual weakening of the Moon's magnetic field over time, as well as its internal cooling processes.
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Why is this important?
In summary, the discovery of the Moon’s solid inner core is a key step in understanding its history and its relationship with our planet. Moreover, by confirming previous discoveries and revealing new details about the Moon’s interior, Arthur Brio and his team are helping us better understand how celestial bodies like the Moon and Earth go through similar processes of formation and evolution.
These findings will help us better prepare for future lunar missions, and the study itself highlights the importance of continuing to explore the Moon’s mysteries, reminding us that even our closest celestial neighbor still has something to surprise us with. In addition, future lunar missions will collect new seismic data that could confirm the findings of Brio and his team.
The Moon's core is very similar to Earth's, with a liquid outer layer and a solid inner core. Image: www.astronomy.com
As such, further research can help to paint a clearer picture of the Moon's interior and answer remaining questions about its formation. The world has thus entered a new era of lunar exploration, which is of paramount importance for both practical applications and scientific knowledge.
Ultimately, the more we know about the Moon's interior, the better we can plan long-term space missions.
We remind you that NASA plans to return humans to the Moon “for the sake of scientific discoveries, economic benefits, and inspiration for a new generation of explorers” during the Artemis mission, which we described in more detail here, and we highly recommend reading it!