A recent study of metal ore deep inside the moon has unveiled evidence that the Earth's natural satellite was created when another planet crashed into Earth a long time ago.
This long-theorized interplanetary collision, which scientists say occurred some 4.5 billion years ago, saw a Mars-sized planet named 'Theia' sever itself into scorching lava shards upon impact with the earth.
Unveiling Theia's Legacy: Evidence Reveals Moon's Origins as Remnants of a Lost Planet
While some of Theia's planetary remains appear to be buried as thick and gigantic 'blobs' deep beneath Africa and the Pacific Ocean's tectonic plates, scientists have yet to find evidence of where the remainder of Theia went following the collision.
However, fresh data from NASA's Gravity Recovery and Interior Laboratory (GRAIL) satellite have discovered enormous quantities of titanium-iron ore deep beneath the moon's surface, indicating that Theia's other remains did, in fact, become Earth's moon.
Adrien Broquet, planetary geophysicist at the German Aerospace Center in Berlin, referred to NASA's GRAIL findings as nothing short of 'mesmerizing.'
His team's new paper, published this April in Nature Geoscience, was centred on 'gravity anomalies' deep under the surface of the moon: dense, heavy pockets of matter identified by the GRAIL spacecraft's sensors.
'Analyzing these variations in the moon's gravity field allowed us to peek under the moon's surface and see what lies beneath,' Broquet stated.
The GRAIL spacecraft discovered two dense zones beneath the moon's crust, in the region known as the mantle, that correspond to the titanium and iron 'ilmenite' deposits that would occur if the Theia impact scenario were right.
Following Theia's anticipated crash with Earth, and after remnants of this lost planet were buried deep beneath the Earth's crust, molten lava pools containing heavy titanium and iron on the moon's surface started sinking deeper into its core, pushing lighter rock up.
'Our moon literally turned itself inside out,' declared Broquet's co-author, Jeff Andrews-Hanna, a geophysicist at the University of Arizona's Lunar and Planetary Laboratory.
Computer models created by their colleague Nan Zhang at Peking University in Beijing provided the initial basis for their theory that titanium-rich material would exist deep within the moon as a result of the moon's formation as fragments of planet Theia.
'When we saw those model predictions,' Andrews-Hanna said, 'it was like a lightbulb went on.'
'We see the exact same pattern when we look at subtle variations in the moon's gravity field,' he said,'revealing a network of dense material lurking below the crust.'
New Findings Illuminate Earth's Ancient History and Moon's Formation
Back on Earth, two comparable dense and peculiar regions near the base of our planet's mantle, known as Large Low Velocity Provinces (LLVPs), have supported the notion that our moon was formed by an interplanetary 'Theia' collision.
One LLVP is located underneath the African tectonic plate and the other beneath the Pacific tectonic plate, according to seismic instruments used to detect earthquakes.
Their presence was confirmed when geologists discovered that seismic waves slowed substantially at a depth of 1,800 miles (2,900 km) in the two zones, which varied from other parts of the Earth.
Scientists believe the material in these LLVPs is 2–3.5 percent denser than the Earth's surrounding core.
Last year, researchers from the California Institute of Technology proposed that these LLVPs originated from a small amount of Theian material that infiltrated the old Earth's lower mantle.
To back this up, they recruited Professor Hongping Deng of the Shanghai Astronomical Observatory to investigate the notion using his pioneering computational fluid dynamics methods.
After completing a series of simulations, Professor Deng discovered that following the moon-forming collision, a large amount of 'Theian' material — approximately 2% of Earth's mass—would have penetrated the ancient planet's lower mantle.
'Through precise analysis of a wider range of rock samples, combined with more refined giant impact models and Earth evolution models, we can infer the material composition and orbital dynamics of the primordial Earth, “Gaia,” and “Theia,”' stated Deng's co-author Qian Yuan, a CalTech geophysicist who also worked on this project.
Deng and Yuan's team published their study in the journal Nature late in 2023.
Broquet hopes that future NASA moon missions, such as the Artemis programme, can collect first-of-its-kind seismic data to support the Theia collision scenario.
'Future missions, such as with a seismic network, would allow a better investigation of the geometry of these structures,' the researcher said.