A chunk of Earth that could be 4.1 billion years old and is described as the planet's "oldest rock," may have been found and dug up on the Moon by Apollo astronauts, according to a new study. The possible relic was discovered and dug up in 1971 and scientists believe that it was sent off Earth, thanks to a powerful impact, possibly an asteroid or a comet. After colliding with the Moon (which at the time was three times closer to the Earth than it is now), it mixed with other lunar surface materials. "It is an extraordinary find that helps paint...