Based on meteorite study, scientists say moon may have formed 4.47 billion years ago after a giant collision between a large proto-planet and the proto-Earth.
Studying shock signatures found in stony meteorites that came from the main asteroid belt, a NASA-funded research team said it has estimated the moon’s age as slightly less than 4.5 billion years, which means 4.47 billion years to be precise.
The moon-forming giant impact was the inner solar system’s biggest and most recent known collision but its timing remained uncertain till now.
“This research is helping to refine our time scales for ‘what happened when’ on other worlds in the solar system,” said Bill Bottke of the Southwest Research Institute (SwRI) in San Antonio, Texas.
The team used numerical simulations to show that the giant impact likely created a disk near the Earth that eventually coalesced to form the moon, while ejecting huge amounts of debris completely out of the Earth-moon system.
It remained a mystery still about the fate of that material but one plausible explanation is that some of it would have blasted other ancient inner-solar-system worlds such as asteroids, leaving behind telltale signs of impact-heating shock on their surfaces.
Subsequent, collisions between asteroids, may be less violent, could have ejected some shocked remnants back to the Earth in the form of fist-sized meteorites, which the scientists said they used for their study.
“By determining the age of the shock signatures on those meteorites, we were able to infer that their origin likely corresponds to the time of the giant impact, and, therefore, to the age of the Moon,” Bottke added.
Once the team concluded that pieces of the moon-forming impact hit main belt asteroids and made ancient impact age signatures in meteorites, they set out to deduce both the timing and the relative magnitude of the bombardment.
The paper has been published in the journal Science.