German researchers have examined moon rocks brought back by Apollo astronauts and found evidence that supports a theory that the moon was formed after Earth collided with a planet-sized body named Theia.
The collision occurred some 4.5 billion years ago, according to ScienceMag.org.
While the collision destroyed Theia, much of its remnants, along with some debris from Earth, eventually came together and led to the formation of the moon.
The findings will likely help scientists better understand the moon's origin.
"We can now be reasonably sure that the giant collision took place," Daniel Herwartz, a geochemist at the University of Cologne in Germany and the study's lead author, said in a statement, according to the Christian Science Monitor.
Meteorites from different parts of the solar system have different proportions of oxygen varieties, also known as isotopes, according to the study.
The computer models that recreated the giant galactic clash indicated that the moon should have a higher portion of Theia in its composition, and a different isotope ratio than that of the Earth, according to ScienceMag.org.
Researchers who studied the Apollo moon rocks previously failed to find any noteworthy difference in isotope ratios between the moon and Earth.
Herwartz and his colleagues used a new approach to look for differences in the ratio of two oxygen isotopes -- oxygen-17 and oxygen-16 -- between moon rocks and Earth rocks.
The researchers were able to extract oxygen samples from all the moon rock samples and discovered that for every million oxygen-16 isotopes, the moon rocks had a dozen more oxygen-17 isotopes than rocks derived from Earth's mantle, according to ScienceMag.org.
This difference "supports the view that the Moon formed by a giant collision of the proto-Earth with (an impactor)," the scientists said in a statement.
The results mean that remnants of Theai account for 40 percent of the moon's composition, meanwhile the Earth is responsible for the rest. Theia likely had a composition resembling a type of meteor called enstatite chondrites, according to the scientists.
"Now that a difference has been found, many will work to confirm or deny it and do battle over what it means," David Stevenson of the California Institute of Technology in Pasadena said to Science.
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