Moon formed 4.47 billion years ago: study

Moon may have been created about 4.47 billion years ago, according to a new study of meteorites that provides clues to the giant collision which formed Earth and the lunar body.
A giant impact between a large protoplanet and the proto-Earth formed the Moon. The timing of this giant impact, however, is uncertain, with the ages of the most ancient lunar samples returned by the Apollo astronauts still being debated.
Research indicates numerous kilometre-sized fragments from the giant impact struck main belt asteroids at much higher velocities than typical main belt collisions, heating the surface and leaving behind a permanent record of the impact event.

Collisions on these asteroids in more recent times delivered these shocked remnants to Earth, which scientists have now used to date the age of the Moon.
By modelling the evolution of giant impact debris over time and fitting the results to ancient impact heat signatures in stony meteorites, the team was able to infer the Moon formed about 4.47 billion years ago, in agreement with many previous estimates.
The most ancient Solar System materials found in meteorites are about one hundred million years older than this age.

The impact signatures provide insights into the last stages of planet formation in the inner solar system.

They can also help researchers deduce the earliest bombardment history of ancient bodies like Vesta, one of the targets of NASA's Dawn mission and a main belt asteroid whose fragments were delivered to Earth in the form of meteorites.
It is even possible that tiny remnants of the Moon-forming impactor or proto-Earth might still be found within meteorites that show signs of shock heating by giant impact debris.
The study was conducted by NASA Solar System Exploration Research Virtual Institute (SSERVI) researchers led by Principal Investigator Bill Bottke of the Institute for the Science of Exploration Targets (ISET) team at the Southwest Research Institute and included Tim Swindle, director of the University of Arizona's Lunar and Planetary Laboratory (LPL).

"Bill Bottke had the idea of looking at the asteroid belt to see what effect a Moon-forming giant impact would have, and realised that you would expect a lot of collisions in the period shortly after that," said Swindle.
"Here at LPL, we had been determining ages of impact events that affected meteorites, and when we got together, we found that our data matched his predictions," he added.
The study was published in the Journal Science.