The moon could have formed when a large protoplanet struck the forming Earth. New research indicates that the collision was energetic enough to completely penetrate the world's materials.
Credit: NASA / GSFC
The collision that created the moon needed to be so strong that it would mimic the material of the young earth and the large body it had made to mingle completely suggests ̵
The insight comes from the largest study to date that compares earth and moon rock, noting that our planet and its natural satellite have a much similar composition as is common between bodies in the solar system.
Richard C. Greenwood, a Research Fellow at the School of Physical Sciences at the Open University in the UK, and his colleagues analyzed rocks from each Apollo mission and compared them to a large collection of rocks emerging from the ocean floor Were taken from the sea. They focused on oxygen, which accounts for up to 50 percent of the analyzed rocks. [Should We Open Some Sealed Apollo Moon Samples?]
"Oxygen is the third most common element in the solar system after hydrogen and helium," said Greenwood, the lead author of the new work, to Space.com. "In general, when a meteorite arrives on Earth, it has a very characteristic oxygen isotopic composition compared to Earth."
"For example, we can very easily identify rocks from Mars by [their] isotopic composition," he added. 19659009] When researchers analyzed Earth and Moon, they found that the oxygen isotopic composition in the samples differed only by 4 parts per million (ppm).
"The proximity of Earth and Moon is extraordinary, said Greenwood. "It really shows that the Earth and the Moon really must have formed during a very, very high energy event that really could mix everything and homogenize everything."
Researchers postulated for the first time in the 1970s that the moon and the earth as we know it originated in a powerful collision between a proto-earth and a body the size of Mars about 4.5 billion years ago, The researchers originally thought that the moon is mainly composed of matter. It was delivered by the impactor and contained a much smaller component of the proto-earth. But if that were really the case, Greenwood said, the oxygen isotopic compositions of Earth and Moon would have to be significantly different, albeit similar in magnitude to the Solar System.
"The original identity of this impactor has been completely lost because it has been completely confused with the material from Earth," said Greenwood.
The tiny difference between the two bodies could be explained by asteroids and meteorites that hit the Earth The Earth has survived since the Moon-forming collision
The similarity of the two bodies also suggests that the water even before the collision on Earth – and more importantly, that it survived the apocalyptic impact. (Some previous work hypothesized that all water was lost and therefore the present water on earth came later.)
"The probable source of water on Earth is carbonaceous chondrites, a type of stone meteorite," Greenwood said , "But they have a very clear oxygen isotopic composition, and if they arrived after this event, we'd see it would make a bigger difference [in the oxygen isotope compositions of Earth and the moon] than it actually is."
The fact that water has survived despite the massive collision on Earth is good news, according to Greenwood. It suggests that the vital substance may be found on suitable planets outside the solar system, despite the fiery process of planetary evolution.
"There are other exoplanets outside the solar system that have been shown to go through in the final stages of their formation a huge impact," said Greenwood.
"Our paper shows that water is really a stubborn stuff, they can totally melt and vaporize your planet, and the water still hangs around."
The new work was published today (March 28) in the journal Science Advances
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