To find the sample’s age, the team looked at bits of the mineral zircon embedded in its structure. ”By determining the age of zircon found in the sample, we were able to pinpoint the age of the host rock at about four billion years old, making it similar to the oldest rocks on Earth,” Nemchin said, adding that “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.”

Earth to Moon

In studying the sample closely, Nemchin and the research team concluded that the rock likely formed at a low temperature in the presence of water and oxygen — conditions commonly associated with Earth that would be extremely strange for the Moon.

It is possible —though quite unlikely — that this lunar rock originated on the Moon. Nemchin posited that perhaps 14321 formed under unusual conditions that appeared only briefly on the lunar surface. “However, a simpler explanation is that this piece was formed on the Earth and brought to the surface of the Moon as a meteorite generated by an asteroid hitting Earth about four billion years ago, and throwing material into space and to the Moon,” Nemchin said. “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.”

If that hypothesis is right, it means that there are likely little bits of Earth scattered all over the Moon.

The findings were published in the journal Earth and Planetary Science Letters.

