The final impact event to affect this sample occurred about 26 million years ago, when an impacting asteroid hit the Moon, producing the small 340 meter-diameter Cone Crater, and excavating the sample back onto the lunar surface where astronauts collected it nearly exactly 48 years ago (January 31-February 6, 1971).
Now, 48 years on, experts are claiming that this relic was once part of Earth after it ended up on the moon after large comet or asteroid collided with the planet. Scientists have discovered the rock decades ago by the Apollo 14 crew.
An global team of scientists associated with the Center for Lunar Science and Exploration (CLSE), part of NASA's Solar System Exploration Research Virtual Institute, found evidence that the rock was launched from Earth by a large impacting asteroid or comet.
"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.
After the sample hit the Moon's surface, "other impact events" helped shape it, including one event some 3.9 billion years ago, the researchers said.
This theory is the easiest explanation since the formation of such a fragment would need an oxidizing environment.
But, they stipulated, it would require the sample to have formed a very deep depth below the surface of the Moon in the lunar mantle. He holds a B.A.in Psychology from the University of Toronto, and a Master of Science in Public Health (M.S.P.H.) from the School of Public Health, Department of Health Administration, at the University of North Carolina at Chapel Hill.
It is possible that the sample is not of terrestrial origin, but instead crystallised on the Moon.
Many researchers believe the moon formed after Earth was hit by a planet the size of Mars billions of years ago.
"The samples of Hadean Earth certainly peppered the lunar surface; other samples will likely be found with additional study".
While moon rocks have been recorded ending up on Earth as a result of asteroid impacts, the reverse had not previously been observed. Therefore, the simplest interpretation is that the sample came from Earth.
Researchers from NASA believe that the impact of the collision jettisoned the rock into space and then landed on the surface of the Moon.
The rock probably stayed buried for eons until around 26 million years ago when another asteroid impact, this time on the moon, produced the 340 m wide Cone Crater.
One of the oldest rocks on Earth may have been dug up on the Moon.
Their findings led them to speculate that the piece of ancient rock was jolted from Earth by an asteroid impact, roughly the size of that which is thought to have killed the dinosaurs.
At an estimated four billion to 4.1 billion years old, the terrestrial zircon mineral found in the sample is now among the oldest known to exist.
By contrast, the terrestrial conditions seem much more likely - even if it seems a spectacular coincidence that this tiny fragment was later returned to Earth.