Well, the verdict is in. Not created by the moon Green cheese After all.
A thorough investigation published in May 2023 found that the Moon’s inner core is a solid ball with a density similar to iron. Researchers hope this will help resolve the long-standing debate about whether the Moon has an inner heart Solid Or Meltedand lead to a more accurate understanding of the history of the Moon – and, by extension, the Solar System.
„Our Results” A team led by astronomer Arthur Priat wrote The French National Center for Scientific Research in France „questioned the evolution of the lunar magnetic field, thanks to the demonstration of the existence of its inner core and supports a global mantle overturning scenario, which brings substantial insights into the chronology of the lunar explosion. The first billion years of the solar system.”
Probing the internal composition of material in the Solar System is most effectively accomplished through seismic data. The way sound waves generated by earthquakes move and reflect off objects inside a planet or moon can help scientists create detailed maps of the object’s interior.
We have lunar seismic data collected by the Apollo missions, but its resolution is too low to accurately determine the position of the inner core. We know there is a liquid outer coreBut what that entails is up for debate. Models of a solid inner core and a completely liquid core work equally well with the Apollo data.
To figure it out once and for all, Priat and his colleagues collected data from space missions. Lunar laser range Experiments to compile a profile of various lunar characteristics. These include the amount of its decay through its gravitational interaction with Earth, the variation with its distance from Earth, and its density.
Next, they performed modeling with different key types to find the closest match to the observational data.
They made several interesting discoveries. First, models that most closely resemble what we know about the Moon describe active inversions deep in the lunar mantle. This means that the denser material on the Moon falls toward the center, and the less dense material rises upward. This function has long been proposed as a way to explain presence of certain elements In the volcanic regions of the Moon. The team’s research adds another point to the number of sources.
And they found that the lunar core is very similar to Earth’s core – with a liquid outer layer and a solid inner core. According to their modeling, the outer core has a radius of about 362 kilometers (225 miles), and the inner core has a radius of about 258 kilometers (160 miles). This is about 15 percent of the full radius of the Moon.
The inner core, the team found, has a density of about 7,822 kilograms per cubic meter. It is very close Iron density.
Interestingly, in 2011 a team led by NASA Marshall Planetary Scientist Renee Weber found a similar result using sophisticated seismic techniques in Apollo data to study the lunar core. They found evidence A solid inner core with a radius of about 240 kilometers and a density of about 8,000 kilograms per cubic meter.
Their results, Priat and his team say, confirm those earlier findings and make a very strong case for an Earth-like lunar core. And this has some interesting implications for the evolution of the Moon.
Shortly after the Moon formed, the Moon had a powerful 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 lunar core is deeply related to how and why the magnetic field disappeared.
Given humanity’s hopes of returning to the Moon in a relatively short time, we won’t have to wait long for seismic verification of these findings.
Published in the thesis Nature.
A version of this article was originally published in May 2023.
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