While it is widely accepted within the scientific community that Moon was formed because of a collision between Earth and a “planetary embryo” approximately 100 million years after the Earth formed, there has been a debate whether the collision was a side-swipe (as shown in the video below) or a head-on collision.
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A UCLA-led research team compared Earth rocks and moon rocks and determined the crash was a head-on collision, not a glancing blow as earlier theories stated.
Previous research from another group in Germany found subtle differences in oxygen isotope ratios between Earth and the moon, differing by about 12 parts per million when it came to oxygen-17. They verified them with UCLA’s new mass spectrometer.
Scientists said more than 99.9 percent of the planet’s oxygen is O-16, which takes its name from the sum of the eight neutrons and eight protons in its atoms.
However, the oxygen on earth also comprises small amounts of the heavier isotopes of O-17 and O-18.
Researchers used to think that earth, Mats and other planetary bodies in our solar system has unique ratio of O-17 to O-16.
“We do not notice any distinction between your Planetis and also the oxygen isotopes in the moon; they truly are not distinguishable”, said Edward Young, a UCLA teacher of cosmochemistry and geochemistry along with cause writer.
Earth’s moon was born from a violent collision between the early Earth and a Mars-size object that scientists call Theia.
However, the UCLA researchers were unable to identify any difference between the moon’s and the Earth’s oxygen isotopes. The fact that the Earth and the moon share the same chemical signatures contradicted the theory.
Scientists knew Earth had been involved in a high-speed crash nearly 4.5 billion years ago, but they thought the crash with Theia had been a 45-degree angle sideswipe. Despite the diversity in oxygen isotopes on the moon, the study made clear that the moon and Earth have the exact same oxygen isotope.
According to the study published on Thursday in the “Science” journal, the striking similarities in the composition of materials from the moon from those in our environment here on Earth strongly suggest that Theia smashed right smack onto our planet. Young and his colleagues believe Theia was almost the same size of the Earth, while some believe it was smaller and approximately similar in size to Mars. Some of these asteroids may have been rich in water, Prof. Collisions of growing bodies occurred very frequently back then, he said, although Mars avoided large collisions. During the same year, Robin Canup of the Southwest Research Institute also proposed such a collision in a separate study.
If that’s the case, the moon and Earth should have a different chemical fingerprint.
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Citation: “Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact”, Edward D. Young, Issaku E. Kohl, Paul H. Warren, David C. Rubie, Seth A. Jacobson & Alessandro Morbidelli.
