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A protoplanet crashed into Earth about 4.5 billion years ago, knocking down a piece of rock that would later become the Moon. Now scientists say remnants of this protoplanet can still be found, lodged deep inside Earth, Science Magazine reported.
If any remnants of the protoplanet, known as Theia, remained after the impact, this may explain why two drops of hot rocks the size of a continent are now found in the Earththe mantle of, one under Africa and the other under the Pacific Ocean. These massive blobs would be around 100 times taller than Mount Everest, if they were ever transported to the Earth’s surface, Previously reported Live Science.
Theia’s impact both shaped the moon and turned the Earth’s surface into an ocean of bubbling magma, and some scientists theorize that the drops formed when this ocean cooled and crystallized, Science reported. . Others believe the drops contain terrestrial rocks that somehow escaped the effects of the collision and nestled undisturbed for millions of years near the center of the planet.
But last week at Lunar and Planetary Sciences Conference, Qian Yuan, a doctoral student in geodynamics at Arizona State University (ASU) Tempe, presented another hypothesis.
Related: Earth has a hidden layer, and no one knows exactly what it is
He proposed that after the lunar impact, dense material from Theia’s mantle descended deep below the Earth’s surface, accumulating in what we now call “the drops.” According to Yuan’s models, rocks 1.5% to 3.5% denser than the earth’s mantle would not mix with the surrounding rock. Rather, they would sink to the bottom of the mantle, near the inner core.
“This crazy idea is at least possible,” Yuan told Science.
A 2019 study, published in the journal Geochemistry, supports the idea that Theia’s mantle was denser than Earth’s – about 2% to 3.5% denser, Science reported. The study authors drew conclusions about Theia’s size and chemical makeup based on an analysis of Apollo moon rocks, which contained a much higher light ratio. hydrogen to the heavy hydrogen that terrestrial rocks they found. (Light and heavy hydrogen differ in the number of neutrons in the nucleus of each atom.)
To provide the moon with so much light hydrogen, Theia had to be very large, almost the size of Earth at the time of impact, and very dry, since the water formed in interstellar space would contain a heavy form of hydrogen called deuterium, which Theia lacked, the authors concluded. Meanwhile, the interior of the towering protoplanet would have held a dense, iron-rich mantle, Science reported.
According to Yuan’s theory, as the lighter rocks rushed through space to form the moon, pieces of the iron-rich mantle rushed towards the Earth’s core as a result of Theia’s impact, where they settled down and formed the enigmatic drops. “I think [the idea is] completely viable until someone tells me it’s not, ”Edward Garnero, a seismologist at ASU Tempe who was not involved in the work, told Science.
However, not everyone is convinced. You can read more about the competing theories on blob formation at Scientific magazine.
Originally posted on Live Science.
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