Scientists discover remains of ‘buried ancient planet’ from 4.5 billion years ago

Scientists have discovered evidence of the remains of a planet within the Moon's crust which they reckon crashed into Earth 4.5 billion years ago.

When space boffins aren't mapping the weather on a 1,250C planet 280 lightyears away or trying to work out if giant explosions from the Sun could scupper expeditions to Mars, they're giving us fascinating insights into the history of our planet.

A longstanding theory about the creation of the Earth and Moon as we know them looks like it's been cemented by the hard work of experts at the National Aeronautics and Space Administration.

Adrien Broquet, a planetary geophysicist at the German Aerospace Center in Berlin, described the findings as completely 'mesmerising'.

How did the Moon form?

It's after NASA's Gravity Recovery and Interior Laboratory spacecraft - or GRAIL - discovered anomalies in the Moon's gravity field in 2011 and 2012 missions

A new study argues this is evidence of huge deposits of the titanium and iron rich mineral ilmenite hidden deep beneath the surface of the Moon.

This is huge and plays directly in to the theory that a Mars-sized planet - dubbed Theia - collided with Earth some 4.5 billion years ago.

In this impact, it is thought the debris smashed off to one side of the planet and formed what we now know as the Moon, getting trapped in the gravitational pull of the Earth.

How the Theia collision could have happened (Hernan Canellas/Arizona State University)

How do we know this is what happened?

Evidence of the impact has already discovered by NASA, with 'basal mantle anomalies' - blobs under the crust of the Earth in the Africa and Pacific Ocean regions - found by scientists and dubbed Large Low Velocity Provinces (LLVPs).

The new discovery on the Moon is a game-changer, with Borquet publishing about this in April in Nature Geoscience.

In his paper, Broquet and his team focus on 'gravity anomalies' that can be found beneath the surface of the Moon.

These are hugely dense pockets of matter that can be detected by GRAIL from space.

Broquet said: "Analysing these variations in the moon's gravity field allowed us to peek under the moon's surface and see what lies beneath."

CGI of the two deposits that have been found under the surface of the Moon, proving the Theia collision to be true (Adrien Broquet&Audrey Lasbordes)

Lead researcher Weigang Liang added: "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, as seen by GRAIL."

So essentially, before scientists were limited to choosing between different hypotheses of what exactly happened after the Moon formed following Earth's collision with another planet 4.5 billion years ago.

Now, for the first time boffins have discovered evidence beneath the Moon's crust of what actually happened.

It follows on from 2023 research from the California Institute of Technology that the LLVPs might have been created by a small amount of matter from Theia entering Earth's lower mantle (about 660 to 2,700 kilometres below the surface).

Professor Hongping Deng, of the Shanghai Astronomical Observatory, carried out a simulation that said the matter from Theia would have settled into Earth's lower mantle after the crash that created the Moon.