An artist’s impression of Earth during the first half billion years of its existence, showing how the planet was bombard in its extreme youth. Those impacts blasted debris into space, some of which likely made its way to the Moon. Image: Simone Marchi.
Researchers have identified what may be the oldest known Earth rock, a fragment that may date back to the so-called Hadean era shortly after the planet’s formation. In a counterintuitive twist, the sample was found not on Earth but on the moon, brought back by the Apollo 14 crew in 1971.
Chemical analysis suggests the rock was blasted into space after a large asteroid or comet smashed into Earth shortly after the birth of the solar system. The rock eventually ended up on the moon, which was three times closer than it is today, about four billion years ago. It then was mixed in with other surface materials, the researchers conclude.
The sample was identified by Research Scientist Jeremy Bellucci and Professor Alexander Nemchin, working at the Swedish Museum of Natural History and Curtin University in Australia, using a new technique for locating fragments of impactors in the lunar regolith.
They found a 2-gram fragment in the ...