The moon may have formed when a large protoplanet smashed into the formation of the Earth. New research suggests that a collision was energetic enough to completely scramble the worlds’ materials.
The collision that the moon should be so powerful that it caused the material of the young Earth and the large body that hit it full mix, new research suggests — and water already on the surface of the Earth to the moon-the form of a crash.
The insight comes from the largest study to date to compare Earth and moon rocks, and find that our planet and its natural satellite to have a much more similar composition than normal between the bodies in the solar system.
Richard C. Greenwood, a research fellow at the School of physical Sciences at the Open University in the united kingdom, and colleagues analyzed rocks from every Apollo mission, and compared these with a large collection of stone from the depths of the ocean and on the seabed. They focused on oxygen, which means that up to 50 percent of the drilled rocks. [Should We Open A Number Of Sealed Apollo Moon Samples?]
“Oxygen is the third most common element in the solar system after hydrogen and helium,” Greenwood, the lead author of the new work, told Space.com. “In general, when a meteorite is on Earth, it has a very characteristic oxygen isotope composition in comparison with the Earth.
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“For example, we can identify rocks of Mars very easily by [their] combination,” he added.
When the researchers analyzed the Earth and the moon rocks, but they find that the oxygen isotope composition of the samples differed by only 4 parts per million (ppm).
“The fact that the Earth and the moon so close is extraordinary,” Greenwood said. “It’s really to show that the Earth and the moon really must have formed, during a couple of very, very high energy impact case, that was really able to mix all the ingredients together and homogenize everything together.”
Researchers first postulated in the 1970s that the moon and the Earth as we know it are created in a powerful collision between a proto-Earth and a body about the size of Mars approximately 4.5 billion years ago. Originally, researchers thought that the moon formed for the most part from material supplied by the influence of the body and contained a much smaller part of the proto-Earth. But if that really was the case, Greenwood said, the oxygen isotope composition of the Earth and the moon should be clearly different — but here they are more comparable by an order of magnitude than anything else in the solar system.
“The original identity of the impactor was completely lost because I completely mixed up with material from the Earth,” Greenwood said.
The minor difference between the two bodies can be explained by asteroids and meteorites that hit the Earth because the moon-forming collision.
The fact that the two bodies are so similar also suggests that the water on Earth already before the collision — and, more importantly, that it survived the apocalyptic smash. (Some previous work the hypothesis that there is no water would be lost, and therefore, the current water on Earth came later.)
“The likely source of water on Earth are carbonaceous chondrites, a type of stony meteorites,” Greenwood said. “But they have a very distinct oxygen isotope composition; if they had arrived after this event, that we would see a bigger difference [in the oxygen isotope compositions of the Earth and the moon] than there actually is.”
The fact that water had survived on Earth, in spite of the massive collision, it is good news, according to Greenwood. It suggests that the life-bearing substance can probably be found in suitable planets outside the solar system, despite the fiery process of planetary evolution.
“There are other planets outside our solar system that have been shown to undergo in the final stages of their formation a very large impact,” Greenwood said.
“But our paper shows that water is actually a very tough stuff. You can completely melt and vaporize your planet and the water is still hanging around.”
The new work is detailed today (March 28) in the journal Science Advances.
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