Apollo 14, the eighth manned mission in the United States Apollo Programme and the third to land on the moon, is most famous for bringing back some of the lunar surface along with it. Inadvertently though, the Alan Shepard-led mission may have brought back some of earth’s surface along with it. Nearly fifty years on, the mission looks to have brought back a piece of rock that originated from the Earth. Published in Earth and Planetary Science Letters, one of the reasons behind the hypothesis that the rock was formed on Earth and then subsequently transported to the moon is backed up by the finding that the core of the rock – made of zircon, quartz and feldspar – was formed on Earth with subsequent formation of the clast geochemistry being on the moon.
The intervening event, scientists have postulated, was a major impact which blasted the rock into space and lodged it into the surface of the moon as a meteorite, where following the highly oxidising conditions of its terrestrial origins, it was subjected to reducing conditions that formed the outer clast. At the time of the blast, the moon was approximately three times closer to the Earth than it is now.
The rock sample, labelled 14321, was studied by researchers at Curtin University in Australia who had acquired it on loan from NASA. Other institutions involved in the research included the Swedish Museum of Natural History, Australian National University, and the Lunar and Planetary Institute in Houston.
Professor Alexander Nemchin, who was the research author for the study said, in a statement “The sample also contains quartz, which is an even more unusual find on the moon. 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. In addition, the chemistry of the zircon in this sample is very different from that of every other zircon grain ever analysed in lunar samples, and remarkably similar to that of zircons found on Earth.”
However, despite the hypothesis that the rock was formed on Earth, Professor Nemchin was cautious in fully guaranteeing an event that could have occurred nearly four billion years ago. “It is possible that some of these unusual conditions (the presence of oxidising conditions and water) could have occurred very locally and very briefly on the moon and the sample is a result of this brief deviation from normality.”
He also went on to say that “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.”
This discovery is a significant one in terms of the light that it can shed on the early origins of Earth and its relationship at the time to other extra-terrestrial objects such as the moon. It also can give rise to further questions on what early Earth was really like and how it evolved to be the planet that it is today.