Below Africa and below the Pacific, there are huge and ghostly masses of superchildren. These are anomalies of high-density rocks that attract and scare geologists at the same time. According to the (old) new hypothesis, these are pieces of the torn protoplanet Theia, which collided with the proto-Earth billions of years ago to form the Moon.
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Africký superchochol. Kredit: Ward et al. (2020), Geochemistry, Geophysics, Geosystems.
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The possibilities to explore the world under our feet are limited. Yet we find incredible things there. For example, there are absolutely gigantic “anomalies,” the vast masses of high-density rock that exist at the bottom of the Earth’s mantle. These are superchools (LLSVP, large low-shear-velocity provinces), one of which is located across Africa and the other below the Pacific Ocean.
Qian Yuan. Kredit: Arizona State University.
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The question is, what are these anomalies? There are a number of hypotheses that are, of course, very difficult to verify in any way. In a recent study, Arizona State University’s team of modelers linked the ghostly superchools to the prevailing and at the same time very viewer-attractive theory of the Moon’s formation during an ancient Earth-Earth collision with a Mars-sized protoplanet called Theia. It was supposed to happen about 4.5 billion years ago, and the Moon then clung from the rubble that remained near the Earth after this immense collision.
A crash you wouldn’t want to experience. Credit: NASA / JPL-Caltech.
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Research leader Qian Yuan and his colleagues are convinced that the Moon is not the only thing left of this planetary collision to this day, apart from the formed Earth as such. Their models show that the superchools mentioned could in fact be pieces of the mantle of the protoplanet Theia. According to them, the mantle of this protoplanet was rich in iron and had a high density. After the protoplanet collision, pieces of Thei’s mantle sank deep into the Earth’s mantle. And after billions of years there are still distinct.
As Yuan points out, the The Giant Impact Formation hypothesis is today all-ranging and mainstream, but with evidence of such an event at the dawn of the solar system, it’s not very general. Yuan and his colleagues found that the mantle of the Theia protoplanet could be about a few percent denser than the Earth’s mantle. Therefore, pieces of the protoplanet’s mantle could dive deep into the Earth’s mantle and create structures there that we observe as superchools due to seismic waves.
The idea that superchools are actually a souvenir from a foreign world is not entirely new. Yuan et al. but so far they have worked the most. Their conclusions are also in line with previous research, according to which certain characteristics of superchools correspond in age to the time before a collision with a protoplanet. Yuan doesn’t hide that it’s an extravagant idea. But he is convinced that it really could have happened. Perhaps further research will suggest more.
Video: 2021_LPSC_Yuan
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