With the help of a "geologic clock", researchers determined that the moon is 4.5 billion years old and formed nearly 100 million years after the start of the solar system.
This conclusion was drawn after researchers examined the growth of many Earth-like planets including Mercury, Venus and Mars in 259 simulation models. They did this by using a disk of thousands of planetary building blocks orbiting the Sun. The analysis led to the discovery that Earth was affected after a Mars-sized object hit it to create the moon. This data was then compared to data that measured the amount of material added to Earth after that impact and a relation between the two was found.
Researchers then created a "geologic clock" that gave a range of when the moon was formed in relation to the beginning of the solar system.
"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," said lead author Seth Jacobson of the Observatory de la Cote d'Azur in Nice, France, in a statement.
Previous studies have provided an estimation of how much material was added to Earth during the Moon-forming impact. Researchers believe that this amount is directly proportional to the amount of highly siderophile elements present in the Earth's mantle.
Analyzing this data, researchers of the current study were able determine that the Moon formed 95 million (±32 million) years after the start of the solar system.
"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," said author Dr. Kevin Walsh from the Southwest Research Institute (SwRI) Space Science and Engineering Division, according to National Geographic.
The small amounts of iridium, platinum and other iron elements in Earth's mantle suggested the formation of the moon took place later than previously thought.
"A late moon-forming event, as suggested by our work, is very consistent with an identical Earth and moon," Jacobson toldSpace.com. "Older disks tend to be dynamically more active, since there are fewer bodies left in the disk to distribute energy amongst."
The findings don't only suggest that the Earth and Moon formed round about the same time but also that planets like Mars and Venus formed just a few million years after the solar system was formed
"This means that Earth and Mars formed over dramatically different timescales, with Mars forming much faster than the Earth," Jacobson said, according to NBC News. "How can this be? Is it just a matter of size? Location? What about Mercury and Venus? Did they grow on similar timescales to the Earth or on timescales more similar to Mars? I think these are some of the really important questions that we, as a community of planetary scientists, will be addressing in the future."
The study was published in the online journal Nature.
