Science has long asserted that our moon was formed after Earth was hit by a planet the size of Mars billions of years ago. This event is known as the giant impact hypothesis.
However, the time of this formation has been fiercely debated, with some scientists believing the formation occurred approximately 30 million years after the birth of the solar system, and others claiming the event happened up to 100 million years later.
We may now have the answer, as a team of international scientists have used measurements from the interior of Earth, coupled with computer simulations, to discover what they say is the ‘geological clock.’
Researchers from France, Germany and the U.S.A carried out 259 computer simulations of the growth of Mercury, Venus, Earth and Mars.
It was during this analysis that the scientists discovered a link between when the Earth was hit, and the amount of material added to Earth after the impact.
This relationship acts very much like a clock which can date the moon-forming event.
Using the ‘geological clock’ system, the researchers found that the moon is 4.51 billion years old, meaning that it formed some 95 million years after the solar system.
It’s being hailed as the first ‘geologic clock’ in early solar system history that does not rely on measurements and interpretations of the radioactive decay of atomic nuclei in order to determine age.
Seth Jacobson of the Observatory de la Cote d’Azur in Nice, France, lead author of the findings, which were published in journal Nature, said: “We were excited to find a ‘clock’ for the formation time of the Moon that didn’t rely on radiometric dating methods.”
“This correlation just jumped out of the simulations and held in each set of old simulations we looked at.”
Researcher and author Dr. Kevin Walsh from the Southwest Research Institute (SwRI) Space Science and Engineering Division said:
“This result is exciting because in the same simulations that can successfully form Mars in only 2 to 5 million years, we can also form the moon at 100 million years.”
“These vastly different timescales have been very hard to capture in simulations.”