Researchers have discovered evidence of the Earth’s oldest rock from the samples brought by the Apollo 14 astronauts in 1971. The rock is expected to be four billion years old and is believed to have reached the Moon by a large asteroid impact, which transferred enough energy to launch a rock from Earth to the Moon. A point to be noted here is that, the Moon at that time was three times closer than it is now.
On Earth, rocks this old have already disintegrated, leaving debris behind. In Australia’s Jack Hills, rocks dating back to 4.4 billion years were found, but they weren’t rocks, it was debris. Scientists believe that the rock on the Moon is more preserved and may contain old minerals.
In the rock fragments brought to Earth, the rock was found to be composed of quartz, feldspar and zircon. These minerals are readily available on Earth but on Moon its kind of unusual. Furthermore, chemical analysis of the fragments showed that they crystallised in an oxidised system at Earth temperatures, rather than Moon’s fluctuating temperature conditions — further proving the point.
Collected by astronaut Alan Shepard of Apollo 14 mission, the rock is named 14321 and is one of the largest bring-backs to Earth. Also, scientists revealed that the rock was formed 20km beneath the Earth’s surface.
While the simple interpretation is that the rock is from Earth, there is a possibility that the rock crystallised on the Moon. It would be unusual, but maybe billions of years ago, the Moon was something different.
There are a lot of mysteries which are yet to be uncovered.