Analysis of lunar soil brought by the astronauts of the Apollo 14 mission showed the presence of mineral particles in one of the samples. According to an international group of scientists from Sweden, Australia, and the USA, the origin of that sample is Earth’s oldest rock found on the lunar surface decades ago.
The article about this discovery was published by the journal “Earth and Planetary Science Letters.” Researchers believe that a part of a meteorite from Earth, which fell on the lunar surface about 3.9 billion years ago, was coincidentally brought up by the Apollo 14 members.
In the studied sample, which was named “Big Bertha”, scientists found fragments of quartz, zircon, and feldspar. The presence of those minerals is quite typical for terrestrial rocks, but not for lunar soil.
Scientists explain that even if we assume the lunar origin of minerals in the sample, they should have been formed at a depth of at least 167 kilometers, which is unlikely. In addition, the formation of those minerals requires oxygen which is only possible on Earth.
So how did Earth’s oldest rock end up in the lunar soil?
Scientists suggest that about 4 billion years ago when the Earth was only about 540 million years, some small celestial body (meteorite or asteroid) could fall on our planet, which raised part of the “breakaway” Earth’s oldest rock into space.
At that time, the Moon was located three times closer to our planet than it is now, so after some time, the rock settled on the satellite surface, specifically in the Cone crater of the Moon, where the Apollo 14 expedition found it.
The discovery of zircon particles in the sample has greatly helped the scientists because this mineral contains uranium, whose half-life is well known.
On this basis, experts have determined that the rock was formed about 4 to 4.1 billion years ago, presumably at a depth of 20 kilometers.
The researchers add that their assumption is the most likely. At least, it is highly doubtful that such “terrestrial” conditions have ever existed on the Moon.
However, for testing the hypothesis, scientists will need new samples of the lunar soil, which may also contain the detected minerals. By the way, in the next decade, scientists may actually be able to get them. NASA plans not only to return a man to the moon but also to gain a foothold there for a long time.