One rock collected on the moon by Apollo 14 astronauts in 1971 has apparently made a rather remarkable journey over the last 4 billion years, from the Earth to the moon and back, reports Phys.org.

Yes, this supposed moon rock is actually an Earth rock. It was likely jettisoned from our planet ages ago, eventually crashing into the moon. From there, it sat for billions of years until two-legged apes in spacesuits picked it up and brought it back home again.

Researchers made the discovery after a new analysis of the rock revealed that it was composed of suspiciously high levels of granite and quartz, which are extremely rare on the moon but relatively common here on Earth. Readings of other materials in the rock, such as zircon, sealed the deal.

"By determining the age of zircon found in the sample, we were able to pinpoint the age of the host rock at about 4 billion years old, making it similar to the oldest rocks on Earth," said professor Alexander Nemchin, author of the paper. "In addition, the chemistry of the zircon in this sample is very different from that of every other zircon grain ever analyzed in lunar samples, and remarkably similar to that of zircons found on Earth."

Well-traveled rock could help us understand Earth

While this might make the rock sound a bit less extraordinary, its ancient Earthly origins make it even more valuable, because scientists could be able to use it to study the conditions on the early Earth.

Figuring out exactly how this Earth rock got mixed up with moon rocks might be more difficult, although there are theories. Rocks can be jettisoned from a planet after an impact with an asteroid, and that's probably what happened with this rock as well. This is also how it's possible for scientists to occasionally find Mars rocks here on Earth, and rocks from other identifiable bodies in the solar system.

"Further impacts on the moon at later times would have mixed the Earth rocks with lunar rocks, including at the future Apollo 14 landing site, where it was collected by astronauts and brought back home to the Earth," explained Nemchin.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

This rock brought back from the moon likely came from Earth
This supposed moon rock is actually an Earth rock. It was likely jettisoned from our planet ages ago, eventually crashing into the moon.