Researchers say that lunar rock samples collected on the Apollo missions aren't old enough to verify the normally accepted 4. According to the commonly accepted hypothesis, the Moon was formed from the debris of a collision between Earth and a smaller planet called Theia , spewing out molten rock that eventually solidified into one whole body that began orbiting Earth.
That means the rock that makes up the Moon came from Earth, and can be used to date it, with some sophisticated modelling. The new study suggests the Moon was created when Earth was almost fully formed.
The models run by Maurice and her colleagues looked at two timescales: how old the Earth was when Theia hit it, and how long the Moon's massive magma ocean took to cool after it had begun to solidify.
That second process took around million years from start to finish, the scientists' models show. Learn about how Earth got its atmosphere and its oceans. These results, which suggest the Earth formed nearly million years after our solar system was born, also throw a monkey wrench into how scientists think about the formation of other rocky planets like Mars and Venus, Jacobson says.
Mars formed a few million years after the birth of the solar system, while Earth clearly took longer, he explains. If Venus formed on a timeline similar to that of Mars, then that would be a "huge puzzle" since Venus and Earth are so similar in terms of mass and orbit.
But these are open questions for future research, Jacobson says. For now, he and his colleagues will continue studying how planets in our solar system formed. All rights reserved. Planetary Weight Gain It's generally accepted that the moon formed near the end of Earth's construction , says Jacobson, when an object about the same mass as Mars hit our planet and blew parts of both bodies into space. A Cascade of Implications This evidence for a later-forming moon means that Earth's impact history was more violent than previously thought, says Jacobson.
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Go Further. Animals Climate change is shrinking many Amazonian birds. Animals Wild Cities This wild African cat has adapted to life in a big city. Animals This frog mysteriously re-evolved a full set of teeth. Rather than study entire rocks and hope they date all the way back to the moon's birth, the team dated the formation of the object's mantle and overlying crust.
This "differentiation" occurred shortly after the giant impact s , when a global liquid-magma ocean initially present on the moon cooled and solidified. And this solidification left a signal, Barboni said — a mineral called zircon. The researchers studied zircon fragments in rocks collected by Apollo 14 astronauts in The team dated the samples radiometrically, by measuring how much of their uranium had decayed into lead, and how their hafnium had decayed into various "daughter isotopes.
The team's analyses show that the zircon fragments are pristine and ancient, dating back to the solidification of the magma ocean, Barboni said. The researchers also managed to correct for the influence of galactic cosmic-ray impacts, which can complicate dating attempts by injecting neutrons into samples, she added. The age the team came up with for the moon — 4.
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