The Moon is the closest thing to the Earth and scientists have been trying to solve the riddle, how it got there and what is its composition?
Researchers are slowly finding answers to this riddle which has troubled scientists for years. The moon has been formed by a head on collision between a young Earth and a Mars-sized forming planet, Theia. Researchers found that the Moon and Earth rocks were similar and indicated that a violent event gave birth to our next door neighbor.

The solar system was formed 4.6 billion years ago. However some 1100 million years after its formation, the neonatal Earth was hit by a Mars-sized rock which was named Theia, after the Greek myth, the mother of the moon. The debris created by this colossal impact later coalesced to form the present day moon. However, there are many questions which need to be answered before we come to these conclusions. It includes the nature of the impact- was it a glancing blow or a straight, high energy impact?

Scientists now contend that the rocks which went on to make the planet and its satellite were thoroughly mixed before they were separated. It also confirms that the impact was straight and a high energy impact. It was the conclusion arrived by lead study author Edward Young, a cosmochemist, and geochemist at the University of California, Los Angeles.

So how did the study conclude that a colossal impact created the moon? The researchers had at their disposal seven moon rock samples collected during the Apollo 12, 15 and 17 lunar missions and an additional lunar meteorite which was a rock which was knocked off the lunar surface by a cosmic event and it later crashed on Earth.

Different planets and Moons have different and distinct isotope signature. The ratio of Oxygen-17 to other isotopes of Oxygen gets smaller for bigger planets and moons. However, the ratios of oxygen-17 to other oxygen isotopes were exactly similar for both Earth and Moon samples. Moon and Earth are more alike isotopically.

The scientists published their findings in Jan. 29 issue of the journal Science.