The Moon 'turned itself inside out' and scientists have just figured out how

It's been a big month for the Moon.

Anyone lucky enough to be in the right place across North America last week saw a total eclipse of the Sun - meaning the Moon entirely covered the Sun's disc - while the University of Arizona has also just published some exciting new research.

The new paper is all about how the Moon 'turned itself inside out'.

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Yes, you read that right - scientists have looked into something truly amazing about how the Moon was formed.

First, let's start with a bit of background. Around 4.5 billion years ago, a small planet collided with Earth, and the resulting molten rock that was flung into space eventually came together and solidified into the Moon.

Researchers from the University of Arizona Lunar and Planetary Laboratory (LPL) have published a paper in Nature Geoscience, looking into exactly how this happened and what happened on the lunar surface.

According to researchers, the Moon likely started life covered by a magma ocean, which cooled and solidified. But things were pretty turbulent under the surface, with leftover bits of magma apparently crystallizing into dense minerals like ilmenite.

"Because these heavy minerals are denser than the mantle underneath, it creates a gravitational instability, and you would expect this layer to sink deeper into the moon's interior," said Weigang Liang, who led the research as part of his doctoral work at LPL.

The paper suggests this dense material sunk further into the Moon's interior, before melting and returning to the surface as titanium-rich lava flows - which are still seen today.

"Our Moon literally turned itself inside out," said co-author and LPL associate professor Jeff Andrews-Hanna.

"But there has been little physical evidence to shed light on the exact sequence of events during this critical phase of lunar history, and there is a lot of disagreement in the details of what went down – literally."

And that's exactly what the researchers set out to solve.

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Liang said: "Our analyses show that the models and data are telling one remarkably consistent story. Ilmenite materials migrated to the near side and sunk into the interior in sheetlike cascades, leaving behind a vestige that causes anomalies in the moon's gravity field."

Scientists looked at the Moon's gravity field, giving them a chance to understand what was going on underneath the surface.

So why is it such a groundbreaking discovery?

"For the first time we have physical evidence showing us what was happening in the Moon’s interior during this critical stage in its evolution, and that's really exciting," Andrews-Hanna said.

"It turns out that the Moon’s earliest history is written below the surface, and it just took the right combination of models and data to unveil that story."

And this could be just the beginning, with future lunar missions likely looking further into what's happening below the Moon's crust.