Evidence of Alien Planet Found in Lunar Rocks
Traces of a non-Earth planet were found in lunar rocks brought back by Apollo astronauts, essentially confirming the theory that the moon was formed by a massive collision between Earth and another planet.
The hypothesis that the moon was formed from a cataclysmic collision has been the accepted theory in the scientific community since the 1980's, but was beginning to decline in favor since before now, analyses of lunar rock never yielded any evidence for this theory (although it was previously supported by computer simulations). It now falls under "Occam's razor" as it is the simplest and most elegant explanation for the newfound evidence. To watch an animation of the collision from the Natural History museum, click here.
"It was getting to the stage where some people were suggesting that the collision had not taken place," lead researcher Daniel Herwartz told BBC News. "But we have now discovered small differences between the Earth and the Moon. This confirms the giant impact hypothesis."
Herwartz et al found these differences using isotopic analysis, or measuring the ratio of different forms of oxygen within the rocks' compositions.
The researchers have aptly named the planet "Theia" after the Titaness in Greek/Roman mythology who gave birth to Selene, goddess of the moon.
Detractors of the collision hypothesis claim that the differences between terrestrial rock and these lunar rocks are small enough that there may be an alternative explanation. For example, the materials that are seemingly of alien origin could have been absorbed by the Moon after it formed.
Professor Alex Halliday of Oxford University is one of these detractors: "What you are looking for is a much bigger difference, because that is what the rest of the Solar System looks like based on meteorite measurements," he said. In other words, the isotopic signature is usually as distinctive as a fingerprint. In the context of this analogy, this would mean that the fingerprints of Earth and Theia would be nearly identical.
But Professor Halliday acknowledges that the surprising similarity between Earth and the proposed Theia does not eliminate the possibility of Theia's existence or the collision. But if the collision did occur, then it is likely that either Theia had a similar composition to Earth because it was formed in very close proximity to Earth, or that the assumption that different planets generally have vastly different "fingerprints" needs to be re-examined.