A layer of iron and other elements deep underground is the evidence scientists have long been looking for to support the giant-impact hypothesis.
Scientists say they have finally found evidence to support the giant-impact hypothesis. The hypothesis suggests that the moon was formed by a massive collision between Earth and a planet about the size of Mars, approximately 4.5 billion years ago. Now, researchers believe that the layer of iron and other elements buried deep inside the Earth also support this explanation.
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Researchers from John Hopkins University simulated the giant impact in the lab and showed that the impact occuring billions of years ago not only sent a huge mass of debris into the space that created the moon, but also formed a stratified layer beneath the Earth’s surface. The layer is evident in seismic data.
The giant impact hypothesis has been a widely accepted theory for how the Earth’s moon was formed. But it is extremely difficult to prove because some 4 billion years ago Earth was very different from what we see today. Researchers think there are still some clues hidden in the chemical composition of our planet, which could be used to support the claim.
“Our experiments bring additional evidence in favor of the giant impact hypothesis," said lead author Maylis Landeau. “They demonstrate that the giant impact scenario also explains the stratification inferred by seismology at the top of the present-day Earth’s core. This result ties the present-day structure of Earth’s core to its formation.”
The stratified layer consists of a mix of iron and lighter elements, including oxygen, sulfur and silicon and clearly points to a massive collision between earth and forming planet. The stratification was possibly the result of the turbulence caused by the giant impact. If Earth was not struck by another cosmic body, it should logically have a homogenous composition not the mix of materials in the layers.
“We're saying this stratified layer might be the smoking gun," said co-author Peter Olson. "Its properties are consistent with it being a vestige of that impact."