This artist's illustration depicts a giant impact between the early Earth and a Mars-size object, a cataclysmic collision thought to have created the moon about 4.5 billion years ago.
Scientists have pinned down the birth date of the moon to within 100 million years of the birth of the solar system — the best timeline yet for the evolution of our planet's natural satellite.
This new discovery about the origin of the moon may help solve a mystery about why the moon and the Earth appear virtually identical in makeup, investigators added.
Scientists have suggested the moon was formed4.5 billion years ago by a gigantic collision between a Mars-size object named Theiaand Earth, a crash that would have largely melted the Earth. This model suggested that more than 40 percent of the moon was made up of debris from this impacting body. (Current theory suggests that Earth experienced several giant impacts during its formation, with the moon-forming impact being the last.) [How the Moon Was Born: A Photo Timeline]
However, researchers suspected Theia was chemically different from Earth. In contrast, recent studies revealed that the moon and Earth appear very similar when it comes to versions of elements called isotopes — more so than might be suggested by the current impact model. (Isotopes of an element have differing numbers of neutrons from one another.)
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