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Remains of Planet That Struck Us and Created the Moon May Still Be Buried in Earth's Mantle

Representative image | NASA/NOAA.

Representative image | NASA/NOAA.

Scientists have said that the Moon was formed when a protoplanet, called Theia, struck Earth in its initial years, around 4.5 billion years ago.

One of the theories of the origin of Earth’s natural satellite Moon is that it was initially a part of our planet. Scientists have said that the Moon was formed when a protoplanet, called Theia, struck Earth in its initial years, around 4.5 billion years ago.

Now the latest study has found Theia’s remains in two continent-sized layers of rock buried deep in Earth’s mantle. In the 52nd Lunar and Planetary Science Conference, held last week, Qian Yuan, a Ph.D. student in geodynamics at Arizona State University, Tempe (ASU) said that for decades, seismologists have questioned two areas that sit below West Africa and the Pacific Ocean and straddle the core like a pair of headphones. Up to 1000 kilometres tall and several times that wide, two continent-sized layers of rock buried deep in Earth’s mantle is the largest thing in the Earth’s mantle.

In the paper, Yuan argues that based on new isotopic evidence and modeling, the large low-shear velocity provinces (LLSVPs) are the guts of the alien impactor itself. Earlier it was believed that the LLSVPs might simply have crystallized out of the depths of Earth’s primordial magma ocean or they might be concentrated puddles of primitive mantle rock that survived the massive impact that led to Moon-forming.

Yuan’s proposal may not be proven completely true, but Sujoy Mukhopadhyay, a geochemist at the University of California (UC), Davis, says that evidence from Iceland and Samoa suggests the LLSVPs have existed since the time the moon came into existence, Science Magazine reports.

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Using the seismic imaging technology, scientists traced the plumes of magma that feed volcanoes on both islands of Iceland and Samoa all the way down to their LLSVPs. And as Science Magazine reports over the past decade, they have discovered that lavas on the islands contain an isotopic record of radioactive elements that were formed only during the first 100 million years of Earth’s history.

Meanwhile, another scientist who was not directly involved with Yuan’s work, Edward Garnero, a seismologist at ASU Tempe, says that it is the first time anyone has presented multiple lines of evidence and created a serious case for this possibility. He says that Yuan’s theory is completely viable until someone tells him it is not.

first published:March 27, 2021, 15:18 IST