While studying the formation of the Moon, astronomers found evidence that was the result around 4.5 billion years ago of the collision of a small planet with Earth. This collision was so violent that Theia, the planet that hit us, ended up fusing with both the Moon and Earth as a result.
The idea that the Moon was formed as result of a planetary crash is not new. However, until now, scientists have thought that Theia has blasted the Moon into orbit after side-swiped Earth and then continued off into space. A research team at the University of California, Los Angeles, suggests now in a press release that Theia actually has fused with Earth and Moon as a result of a head-on collision.
According to Science Alert, the research team studied six volcanic rocks from Earth's mantle and seven lunar rocks brought back to Earth by the Apollo missions. The scientists analyzed which oxygen isotopes the rocks contained by counting the number of protons and neutrons in oxygen atoms. The rocks on each planetary body has a unique 'fingerprint' ratio of oxygen isotopes and that can allow scientists to locate where they came from.
Earth and Moon rocks would have different oxygen isotope ratios and the Moon would be made up mainly of Theia if the planet simply side-swiped Earth and produced the Moon. However, the scientists found that this hypothesis is not verifying. According to the lead researcher Edward Young, the research team could not find any difference between Earth's and the Moon's oxygen isotopes.
Another hypothesis was proposed back in the year 2012, stating that, rather than a side-swipe, Earth and Theia were involved in a head-on collision and ended up fusing together as a result. The findings of the new study back up that previous hypothesis.
Young declared that the research team did not find a different signature of Theia in the Moon versus Earth. This means that "Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them."
