The early days of Earth were so chaotic that it is difficult to believe that life ever began here. What is now the beautiful blue marble we live in was once an apocalyptic wasteland with a molten surface and an atmosphere severely lacking oxygen. Almost all evidence of this fiery first era of the planet, called “proto-Earth”, has long disappeared. However, there is one chemical residue that has just come to light.
new study published in Nature has discovered the only remaining known piece of proto-Earth: a chemical signature hidden in some of the oldest surviving rocks on the planet.
Researchers believe the imbalance of potassium isotopes in these rocks is a relic of Earth's oldest environment that was never wiped out.
Giant Impact that Hit Proto-Earth
The solar system materialized about 4.6 billion years ago when gas and dust formed a spinning disk that later became the solar nebula. Much of this primordial material was pulled toward the center, giving rise to the Sun. The remaining gas and dust coalesced at different points to form each planet, including Earth.
Proto-Earth was unable to support life. In addition to the hot and hostile conditions, the young planet was under constant pressure from asteroid impacts. At one crucial moment, a meteorite the size of Mars (sometimes called “Theia”) fell on him. This giant impact will change the trajectory of our planet.
After being beaten by Theia, the bowels of the Earth melted and fell into disarray. The environment that was once Proto-Earth has completely changed, with almost all the material evaporating. There is a silver lining to this brutal chapter of Earth's history: we have to give thanks for releasing the rubble that would become Moon.
Read more: The origin of water on Earth may not have started with an asteroid impact
Chemical remains of proto-earth
The Earth struggled after the giant impact, but its surface eventually cooled and hardened. It seemed that the material from the Proto-Earth had disappeared forever.
However, a new study seems to prove that this is not the case. When the researchers examined rock samples in Greenland and Canada, as well as lava deposits in Hawaii that emerged from the mantle, they discovered an unusual imbalance in the isotope potassium-40.
Previously, researchers discovered a similar imbalance in meteorites that did not have the current composition of the Earth. The same imbalance in ancient rocks and lava deposits suggests they contain material that originated from Proto-Earth before Theia's impact.
“This may be the first direct evidence that we preserved proto-Earth materials,” said author Nicole Nee, a professor of Earth and planetary sciences at the Massachusetts Institute of Technology, in her paper. statement. “We are seeing part of a very ancient Earth, even before the giant impact. This is surprising because we expect this very early signature to be slowly erased as the Earth evolves.”
Meteorite modeling
After testing rock and lava samples, the researchers noticed a specific deficiency in the isotope potassium-40, a feature that set these materials apart from everything else found on Earth.
If the Proto-Earth were truly composed of potassium-40-deficient materials, these materials would have undergone chemical changes as a result of meteorite impacts (including giant impacts). With this in mind, the researchers used data from all known meteorites and tested simulations of meteorite impacts on the early Earth. As a result of the modeling, compositions corresponding to most modern materials on Earth were obtained.
This confirms the fact that samples of ancient rocks and lava somehow held the remains of Proto-Earth while everything around them changed after a giant impact.
No meteoritesHowever, they have been shown to have the same potassium isotope deficiency as these Proto-Earth samples. Thus, there may still be additional clues pointing to Proto-Earth.
“Scientists have tried to understand the original chemical composition of the Earth by combining the compositions of different groups of meteorites,” Ni said. “But our research shows that the current inventory of meteorites is not complete, and there is still much to learn about where our planet came from.”
Read more: The Earth was formed 4.54 billion years ago – how do scientists know?
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