Some 4.5 billion years ago, an object the size of Mars smashed into the embryonic Earth. This devastating collision created a debris field around our young planet that eventually coalesced into the Moon
By Becky Ferreira | MOTHERBOARD
This idea, called the giant impact hypothesis, has accumulated compelling evidence, but there are still missing pieces of the puzzle. For instance, it does not fully account for the near-identical isotopic signatures of Earth and the Moon (meaning they are made of the same material). If a Mars-sized impactor really did wallop our planet during its infancy, it’s odd that it didn’t contribute more of its own debris to the fallout.
A study published on Monday in Nature Geoscience suggests that this incongruity could be explained if the Moon was formed as a result of around 20 smaller impacts, instead of one colossal dust-up between worlds.