Melbourne, Mar 26 (ANI): A new study conducted by scientists has raised new questions about the birth of the Moon after samples from Earth and the lunar surface were found to be virtually identical.
The study contradicts the theory that the Moon formed after the impact of a Mars-sized object named Theia with the early Earth about 4.5 billion years ago.
At the time both the Earth and Theia were still partially molten, the impact causing Theia's core to sink into the Earth's core, while lighter ejecta and debris was thrown into space eventually coalescing to form the Moon.
The new study, conducted by Junjun Zhang and colleagues from the University of Chicago, compared isotopic ratios of titanium in lunar and terrestrial samples.
They found that the ratio of titanium isotopes on both Earth and the Moon to be identical to within about four parts per million.
Since the Mars-sized impactor is expected to have been isotopically different, the measurements suggest the Moon is either made entirely of material from Earth, or intense mixing occurred on both bodies after impact.
According to the researchers, the similarity cannot be explained by both bodies forming in the same part of the solar system because meteorite samples show extensive diversity in titanium isotopic ratios.
They conclude that the isotopes are far more likely to have come from Earth rather than another planet.
Brad Carter, Planetary scientist from the University of Southern Queensland said that while it's unlikely to have two planets with the same chemical composition, it's not impossible.
"Despite what the paper says, a planet forming very close to the early Earth could have a similar composition resulting in similar isotopic ratios," ABC Science quoted him as saying.
"It's also possible that Theia was essentially made of ice, something from the Kuiper belt in the outer solar system.
"This would have provided the energy of impact, but with the ice evaporating away leaving Earth material to eject into space and form the moon," he said.
Another option suggested by Zhang and colleagues involved the proto-Earth spinning much faster than previously thought, allowing a greater degree of mixing.
"However we don't really think Earth had spun rapidly enough for that to happen.
"And then you have the problem of slowing down the Earth's rotation afterwards.
"Zhang and colleagues suggest a gravitational resonance effect between the Earth, Moon and Sun may have provided the forces needed to slow down the Earth's spin rate," Carter added.
The study has been published in the journal Nature Geoscience. (ANI)
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