What are the huge mysterious blobs near Earth’s core?

Deep near the Earth's centre, two continent-sized blobs of strange material were discovered in the 1980s by geophysicists. One was found under the Pacific Ocean and the other beneath the African continent.

The composition of each blob is probably different from the mantle surrounding it, considering that it is twice as large as the Moon.

Since then, many researchers have tried to unravel this mystery of planetary science. A new study also offers a solution.

Let’s take a look.

What are these strange blobs?

Formally, these puzzling blobs are known as large velocity provinces (LLVPs).

They were initially discovered by scientists using the measurement of seismic waves passing through the Earth.

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Seismic waves go through various materials at varying speeds, and in the 1980s, the first indications of significant three-dimensional fluctuations on a massive scale deep beneath the Earth's structure emerged, according to Astrobiology.com.

The seismic wave pattern in the deepest mantle is dominated by the traces of two massive formations close to the Earth's core, which scientists think have an extremely high iron content.

The report explained the areas have a higher density than the surrounding areas due to their high iron concentration, which slows down seismic waves travelling through them, hence the term "large low velocity provinces."

How were they formed?

The Mars-sized blobs buried far below the Earth's mantle caught the attention of an international team of Caltech researchers, who published it in the journal Nature on 1 November.

According to them, the two blobs may be the remains of a prototype planet that made a massive influence on Earth billions of years ago, which also produced our Moon.

The Moon was created around 4.5 billion years ago, according to long-held theories, following a massive impact between Earth and a smaller planet called Theia, as per The Guardian. However, no evidence of Theia has ever been discovered in meteorites or the asteroid belt.

According to the latest theory, the majority of Theia was absorbed by Earth, which at the time was still a young planet and only accounted for 85 per cent of its current size, creating the LLVPs, while the Moon was formed by the remaining impact debris.

The large impact hypothesis is appealing to many scientists, but they are still looking for evidence to back up the theory.

Among the signs of a severe collision that could still be there today are any hallmarks.

The impact would have melted the top layer of the Earth's mantle, allowing a sizable portion of Theia — roughly 10 per cent of the planet — to pierce further into the globe and eventually descend into the core.

The rock from Theia may have drifted around due to convection inside Earth during the course of the following 4.5 billion years, eventually forming the blobs that are there today. About 1,800 miles below the surface, the blobs sit close to the Earth's core boundary and are estimated to be slightly denser than the surrounding mantle rock.

A portion of the mantle from Theia may have merged with the Earth's, eventually clumping and crystallising to create the two separate blobs that are now visible at the mantle-core border; other collision debris combined to produce the Moon.

“To my knowledge, our work is the first one proposing this idea,” Qian Yuan, the lead author of the study and a geophysicist by training, told The Guardian.

To determine whether the buried blobs are, in fact, relics of an ancient Theia, scientists may need a good supply of moon rocks.

“I look forward to seeing future missions on the moon to bring back its mantle rocks, which are very likely to come from the impactor Theia, according to the majority of moon-forming impact simulations,” Yuan said, adding, “If the lunar mantle rock and LLVP-related basalts share the same chemical signatures, they should both originate from Theia.”

With inputs from agencies