Age dating meteorites
The simulations found that numerous fragments from the moon-forming impact — hundreds of millions of which were at least a mile (1.6 kilometers) long — blasted the asteroid belt, striking asteroids there at speeds of more than 22,370 mph (36,000 km/h), more than twice as fast as typical crashes in the belt.
These collisions from the moon-forming impact would have generated superheated material, the researchers said.
"This gives us a new window on a time period which has been virtually unknown up to now." This research "raises the intriguing possibility that trace amounts of the primordial Earth or moon-forming impactor called Theia may still be found on asteroids today, or possibly within some of our meteorites," Bottke said.
"It may be simply a matter of looking and asking the right questions.
The commonly accepted 4.5 billion year age of the earth is derived from radiometric dating of lunar rocks and meteorites in addition to dating methods based on the Gerling-Holmes-Houtermans model. Those who developed the method utilized Pb, lead isotopes that are the product of radioactive decay, normalized to 204Pb.
The leading explanation for the moon's origin, known as the giant impact hypothesis, suggests that the moon resulted from the collision of two protoplanets, or embryonic worlds.
Here, the 'innocent bystanders' were the main-belt asteroids." Collisions against these asteroids in more recent times returned these remnants to Earth in stony meteorites, which the scientists now have analyzed and used to date the age of the impact.