Oldest piece of Earth found on moon

So when the Apollo 14 astronauts collected it nearly exactly 48 years ago - between January 31 and February 6, 1971 - they thought it was an organic sample that would provide information about the moon and its composition.

An analysis of the rock revealed that it formed at temperatures associated with Earth and in an Earth-like setting combined with oxygen.

One of the oldest rocks on Earth may have been dug up on the Moon.

While moon rocks have been recorded ending up on Earth as a result of asteroid impacts, the reverse had not previously been observed.

Kring noted, "The conclusion of a terrestrial origin for the rock fragment will be controversial".

If we ever go back to the moon again, we might find more Earth samples lying around the surface.

Katie Robinson, a postdoctoral fellow at the LPI-JSC Center for Lunar Science and Exploration and a co-author of the new study, said sample 14321 has been recognised as being unusual for a long time - and only now are we appreciating how unusual it really is.

The scientists found that one rock contained a 0.08-ounce (2 grams) fragment composed of quartz, feldspar and zircon, all of which are rare on the moon but common here on Earth.

It was then returned to the surface around 26 million years ago, during the impact event that produced the Cone Crater - where it remained until Big Bertha was collected by Apollo 14 astronauts just a few decades ago.

Dr Gernon, Associate Professor in Earth Science at Southampton University, said: "The Moon is our nearest neighbour so gets hits by the same population of asteroids". The impact probably melted the fragment, buried by another collision almost 3.9 billion years ago and uncovered by another impact 26 million years ago. Experts do not exclude the possibility that the stone did not originate on Earth, but this version in serious doubt: then the element for crystallization it was necessary to be in the depths of the lunar mantle. "After all, as this paper shows in 2019, we are still making discoveries about the Moon from rocks collected 48 years ago".

Scientists believe that the moon itself was formed around 4.5 billion years ago as a result of a collision between the Earth and another astronomical body approximately the size of Mars.

The evidence suggests the rock crystallized below Earth's surface between 4 billion and 4.1 billion years ago, during the Hadean Eon, when the fledgling Earth was regularly struck by large objects. The sliver of material, the same width as two human hairs, has been dated to 4.4 billion years old. "There are zircons on Earth of 4.4 to 4.3 billion years old which come from western Australia".

The researchers believe that this impact helped bring the piece of Earth back to the moon's surface.

The team acknowledged that the fragment could have formed deep beneath the moon's surface, but it's much more likely it formed on Earth. The sample would also have had to have been created at a tremendous depth, where different compositions are anticipated, if that were the case.