Earth’s moon was most likely formed after our planet collided with another roughly the size of Mars billions of years ago. The exact time of this incident—and the moon’s “birth”—has long been the subject of debate. Until now.
By comparing measurements from the interior of Earth with computer-simulated data, an international team of planetary researchers has calculated the date to be within 100 million years of the birth of our solar system. Calling it a “geological clock,” the scientists say it is the most accurate timeline yet on the creation of Earth’s sole natural satellite.
It has long been speculated that the moon was formed by the massive collision between Earth and another planet-like body called Theia. The newly created model suggests that more than 40% of the moon is made up of debris from Theia, which was otherwise destroyed by the collision.
Scientists suspect that Theia was very different in its chemical makeup than Earth. However, recent studies have revealed that Earth and the moon share a virtually identical chemical makeup, particularly in their elemental isotopes.
“This means that at the atomic level, the Earth and the moon are identical. This new information challenged the giant impact theory […],” Seth Jacobson, the study’s lead author and a planetary scientist at Cote d’Azur Observatory in Nice, France, told Space.com.
Jacobson stated that, while no one seriously disputed that a planetary impact was the most likely scenario for the moon’s formation, the close atomic similarities between Earth and the moon put into question the circumstances of the collision.
Current theories suggest that Earth experienced several similarly-huge impacts during its formative era, with the moon-forming collision being the last. By pinpointing when the moon formed, the planetary research team can better explain the mysterious similarities between the satellite and Earth.
Previous efforts to calculate the moon’s age have returned various results, ranging from 30 million to 100 million years after our solar system’s creation. To find a more accurate date, Jacobson et al simulated the growth of the solar system’s rocky planets (Mercury, Venus, Earth, and Mars).
Analyzing this planetary formation through more than 250 computer simulations, the team found that the amount and makeup of the material accreted onto Earth following its impact with Theia would vary greatly based on when it occurred in the proposed timeline. The presence of certain minerals in the earth’s core, such as iridium and platinum, suggests that the moon-forming event took place later than previously hypothesized.
The team’s findings date the creation to about 95 million years (give or take 32 million) after the formation of the solar system itself. “A late moon-forming event, as suggested by our work, is very consistent with an identical Earth and Moon,” Jacobson said.
The research team’s complete report can be found in the 3 April 2014 issue of the journal Nature.
- “Moon’s age revealed: ‘Geological clock’ shows satellite is 4.51 billion years old” http://www.dailymail.co.uk/sciencetech/article-2595379/Moons-age-revealed-Geological-clock-shows-satellite-4-51-billion-years-old.html
- “How old is the moon? True age is finally revealed” http://www.independent.co.uk/news/science/how-old-is-the-moon-true-age-is-finally-revealed-9236150.html
- “The Moon’s real age is finally revealed, but the mystery of Earth’s tardy development lives on” http://www.extremetech.com/extreme/179768-the-moons-real-age-is-finally-revealed-but-the-mystery-of-earths-tardy-development-lives-on