A Creative Collision

A new study supports the theory that Earth helped create the Moon

June 09, 2014
Jurgen & Christine Sohns—Getty Images

New evidence indicates that the moon is the result of an ancient collision between Earth and another planet.

Looking up at the sky on a clear night, the moon may seem like it is a universe away.  At a distance of more than 238,000 miles from our little blue planet, it practically is. But there was once a time the Earth and the moon were not so far apart.

A new analysis of moon rocks, published in the journal Science, is revealing some interesting clues about the ancient history of the Earth. These clues support the theory that the Earth and moon may, in fact, be family.

The chemical composition of moon rocks can reveal how they were created.

Alexander Klein—AFP/Getty Images
The chemical composition of moon rocks can reveal how they were created.

The Impact Theory

Researchers have long speculated that a planet called Theia collided with Earth about 4.5 billion years ago. Theia was destroyed in the crash, but Earth survived with just a few broken parts. Theorists believe that the remains from the collision joined together and eventually formed the moon. However, no hard evidence to confirm this theory has been found until now.

Previous studies of these specimens, collected by NASA’s Apollo missions, have shown little to support the collision theory. But according to this recent study, an examination of different types of oxygen, called isotopes, found in the moon rocks, reveals traces of both the moon and Theia. They also contain elements of a rare form of meteorite not found on Earth, suggesting they must have come from another celestial body. “We have now discovered small differences between the Earth and the Moon," Dr. Daniel Herwartz, lead author of the study, told BBC news. “This confirms the giant impact hypothesis.”

When it first formed, the moon was just 14,000 miles away from us. Although the two celestial bodies are locked in orbit, the moon is slowly inching away from Earth at a rate of about 3.8 cm a year. Though it may be moving farther from us in distance, this new evidence makes the origin of the moon feel very close to home.

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