The moon was formed nearly 100 million years after the start of the solar system, a study released this week indicates.

Researchers came to the conclusion after analyzing the growth of Earth-like planets such as Mercury, Venus and Mars. Using their growth history from 259 simulations, they found that Earth was affected after a Mars-sized object hit it to create the moon. To find when this happened, researchers 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," Seth Jacobson of the Observatory de la Cote d'Azur in Nice, France, and lead author of the study published in Nature said in a statement.

The clock is the first to not rely on radioactive dating but to use independent and direct measurements to determine the moon's age. The method involved the relationship between Earth’s crust and its affinity for combining with iron, an element that came after the last giant impact, National Geographic reports.

The new study contradicts past findings that have suggested Earth experienced several impacts with the last credited with forming the moon. New findings say the moon was formed 4.5 billion years ago by a Mars-size object named Theiaand.

Researchers took into consideration the amount of iron material accreted onto Earth after the moon-forming impact. If the impact was late, the amount would be small and vice versa. Since only small amounts of iridium, platinum and other iron elements were found on Earth’s mantle, this suggested the event that formed 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 told Space.com.

Other findings suggested the event was fast and more energetic, another sign that it took place later.

"Older disks tend to be dynamically more active, since there are fewer bodies left in the disk to distribute energy amongst," Jacobson said.

The implications for the study are vast, not only suggesting the moon and Earth formed together but that planets like Mars was formed just a few million years after the solar system came into being. While some questions may be answered, there are still many more stones left unturned.

"This means that Earth and Mars formed over dramatically different timescales, with Mars forming much faster than the Earth," Jacobson said. "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."

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