Jakarta –
A study revealed that the remnants of the protoplanet that hit Earth and created the Moon may still be hiding deep in Earth’s mantle.
The scientists’ study shows that this impact, which hit the newly formed Earth 4.5 billion years ago, is still present in the Earth’s mantle as two mysterious ‘blobs’ that have long puzzled geoscientists.
These clumps, known as large low-shear-velocity provinces (LLVP), are where seismic waves move more slowly than the rest of the mantle, indicating differences in temperature, composition, or both.
Together, these clumps make up about 4% of the mantle, one under Africa and the other under the Pacific Ocean.
“The impact of the formation of the Moon is a very likely explanation for the origin of these two plumes,” said study first author Qian Yuan, a geophysicist at the California Institute of Technology, as quoted by Live Science.
In a new study published November 1, 2023 in the journal Nature Climate Change, Yuan collaborated with planetary scientists to simulate the impact of the Moon’s formation, its impact on Earth’s mantle, and how the remains of impacted objects circulated within the mantle over 4.5 billion years. forward.
They first discovered that a collision of Earth with an object the size of Mars, the size of the accepted impact, would not melt the entire mantle, but only the top half.
“The dense underlayer will cover more than 10% of the impact mantle. This impact chunk, in terms of mass and volume, is very comparable to the two mantle plumes we see today on Earth,” Yuan explained.
Modeling of mantle circulation suggests that the impact could gradually merge with Earth’s mantle. Because its density is about 2.5% that of the mantle, according to the model, it will sink and solidify, then eventually stabilize at the bottom of the mantle but not merge with the Earth’s core.
This is also consistent with what is seen in the mantle plume today, which is at a depth of more than 2,000 km and is about 3% denser than the surrounding environment.
“Because its density is higher, it will allow it to remain above the Earth’s core-mantle boundary for 4.5 billion years,” Yuan said.
Contains the beginning of Earth’s history
Other recent studies also suggest the possibility that giant impacts could explain the LLVP, although they do not specifically address the impact of the Moon’s formation.
The research, published last October in the journal PNAS, also modeled mantle circulation and found that precious metals brought to Earth by past impacts could remain in the LLVP today.
“It is possible that the LLVP contains material from multiple impacts that occurred early in Earth’s history,” Yuan and his colleagues wrote in their study.
“Mantle plumes are important, because their boundaries correlate with mantle plumes, where the magma is hotter than the surrounding region. Mantle plumes, in turn, correlate with hot spots of volcanism, including diamond-bearing eruptions called kimberlites,” Yuan said.
Volcanic activity provides the only glimpse into the geochemistry of mantle plumes, because volcanic rocks called basalt that erupt in the area may retain traces of magma from the plumes.
Most of the impacts that formed the Moon formed Earth’s natural satellite. So, comparing these rocks with Moon rocks can reveal whether they come from the same source.
But for that, researchers need samples from the Moon’s interior, something that might be possible with the planned Artemis crewed mission to the Moon.
“Future missions to the Moon could test this hypothesis,” Yuan said.
Watch Video “China Accelerates Fourth Phase of Lunar Exploration Project”
(rns/rns)
2023-11-03 23:15:45
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