Giant impact hypothesis: Traces of Theia planet found on the Moon

Evidence of the world that crashed into the Earth billions of years ago to form the Moon has been found after researchers analyzed the lunar rock brought back by Apollo astronauts .

Analysis of lunar rock shows traces of the “planet” called Theia.

The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision.

The study has been published in the journal Science.

The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia planet 4.5 billion years ago.

Theia was named after a goddess in Greek mythology who was said to be the mother Selene the goddess of the Moon. It is thought to have disintegrated on impact with the resulting debris mingling with that from the Earth and coalescing into the Moon.

It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no one had found any evidence of Theia in lunar rock samples.

Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia

Now a more refined analysis of Moon rock has found evidence of material thought to have an alien origin.

According to the lead researcher, Dr. Daniel Herwartz, from the University of Goettingen, no one has found definitive evidence for the collision theory, until now.

But the difference, some say, could be explained by material absorbed by the Earth after the Moon formed.

Dr. Daniel Herwartz measured the difference in what is called the isotopic composition of the oxygen contained in rocks on Earth and Moon rock. This is the ratio of different forms of oxygen.

Studies of meteorites from Mars and the outer solar system show that these ratios are markedly different -rather like a fingerprint.

One possibility is that Theia was formed very close the Earth and so had a similar composition. If that was the case it raises the possibility that the assumption that each planet in the current Solar System has a markedly different fingerprint that needs to be revisited.