4.2 billion years ago, the moon probably turned itself inside

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In a new study published Monday in Nature Geoscience, the researchers looked at subtle variations in the Moon’s gravitational field to provide the first physical evidence of a sinking mineral-rich layer.
In 2011, a pair of NASA spacecraft began orbiting the Moon to create a map of its gravitational field.
As this ocean cooled and solidified, the less dense layers at the top began crystalizing, forming the Moon’s mantle and the crust.
Beneath the surface and closer to the Moon’s core, however, the more dense layers took longer to crystalize.
Those layers were heavy with iron and titanium, and because they were more dense than the layers above them, they sunk deeper into the Moon’s interior.
As they did that, the mineral-rich, dense layers mixed with the mantle of the Moon, melted, and then returned to the lunar surface as titanium-rich lava flows (which we still see today).
This theory of the Moon overturning has been around since the days of Apollo, when astronauts collected samples from the Moon and found high concentrations of titanium.
The recent study, however, is the first to tackle the formation model using the Moon’s subtle gravitational anomalies.


The Moon may have gone through a dramatic process in its early formation when a dense layer of material sank deeper into the moon’s interior, mixed with the lunar mantle, and eventually returned to the surface.

One of the most bizarre formation theories for the Moon, which postulates that Earth’s natural satellite may have turned inside out a few million years after it originated, is supported by new evidence discovered by a team of researchers from the University of Arizona. In a recent study, which was published on Monday in Nature Geoscience, the scientists examined minute changes in the gravitational field of the Moon to offer the first tangible proof of a layer rich in minerals that is sinking.

In order to map the Moon’s gravitational field, two NASA spacecraft started orbiting it in 2011. Due to gravitational anomalies, one of the spacecraft on the GRAIL mission (Gravity Recovery and Interior Laboratory) would accelerate when passing over specific areas of the Moon.

Adrien Broquet, a co-author of the study and researcher at the German Aerospace Center in Berlin, told Gizmodo that “these gravity anomalies are indicating the presence of these dense rocks that are about 24 miles (40 kilometers) deep into the lunar interior.”. Therefore, we connected these rocks to the Moon’s entire evolutionary history and believe that they are the remains of the Moon’s early, dynamic phase. “.

There was a magma ocean surrounding the Moon when it first formed. The less thick layers at the top of the ocean started to crystallize as it cooled and solidified, forming the Moon’s crust and mantle. However, the denser layers below the surface and nearer the Moon’s core took longer to crystallize. These layers sank farther into the Moon’s interior because they were denser than the layers above them and contained a lot of iron and titanium. In the process, the dense, mineral-rich layers mixed with the Moon’s mantle, melted, and returned to the surface as titanium-rich lava flows, which are still visible today.

Since astronauts collected samples from the Moon during the Apollo era and discovered high concentrations of titanium, there has been a theory that the Moon is overturning. It is the first study, though, to address the formation model with the Moon’s faint gravitational anomalies.

NASA’s new crew will gather more evidence to help us understand the origins of our natural satellite as they get ready to land on the Moon for the upcoming Artemis missions.

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