2023-11-03 12:00:06
In the depths of the Earth’s mantle are hidden the remains of a protoplanet which struck the Earth, constituting the event at the origin of the creation of the Moon. This hypothesis, supported by a new study, might solve a long-standing geological puzzle.
“Blocks” known as low shear velocity provinces (LLVPs) mark the Earth’s mantle. Seismic waves travel less quickly, which suggests differences in temperature. a thermometer and…) or composition. These zones, under Africa (With an area of ​​30,221,532 km2 including the islands,…) and the Pacific, make up approximately 4% of the mantle.
Credit: Hernán Cañellas
Qian Yuan, a geophysicist at the California Institute of Technology, presents collision as a plausible explanation for these LLVPs. Their study, published in the journal Nature Climate Change, simulates the impact and its influence on the mantle. This suggests that the collision with the protoplanet, named Theia and the size of Mars, would not have melted the entire mantle but only its upper half.
More than 10% of the impactor mantle would thus have been captured, in agreement with the mass of the LLVPs observed. The model indicates that this portion, 2.5% denser than the surrounding mantle, would have sunk and then solidified, remaining above the core-mantle boundary for 4.5 billion years.
LLVPs are also intriguing for their geochemical role. Mantle plumes, hotter than the rest of the mantle and associated with volcanic hot spots, are influenced by these structures. The volcanic basalts, erupting above the LLVPs, might contain traces of this ancient impact.
A large part of the material from the impactor having formed the Moon (The Moon is the only natural satellite of the Earth and the fifth largest satellite of the…), the comparative analysis of lunar and terrestrial rocks might confirm if they share a common origin. Future lunar missions, such as Artemis, might test this hypothesis by taking samples.
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