Earth’s early days were so chaotic that it’s hard to believe life began here at all. What is now the beautiful blue marble we live in was once an apocalyptic wasteland with a molten surface and an atmosphere severely lacking in oxygen. Almost all evidence from this fiery first era of the planet, referred to as “primordial Earth,” has long disappeared. However, there is one chemical left, which has just appeared.
new He studies Published in Natural Earth Sciences It has revealed the only known remaining piece of proto-Earth: a chemical signature hidden in some of the oldest preserved rocks on the planet.
Researchers believe that the imbalance in potassium isotopes within these rocks is a remnant of Earth’s early environment that was never erased.
The giant impact that struck the primordial Earth
The solar system originated about 4.6 billion years ago, when gas and dust formed into a rotating disk that later became the solar nebula. Most of this primordial matter was drawn to the center, giving rise to the Sun. The remaining gas and dust collected at different points to form each planet, including Earth.
The proto-Earth was not in a position to support life. In addition to its hot and hostile conditions, the young planet was under constant pressure from asteroid impacts. At one climatic stage, it was struck by a Mars-sized meteorite (sometimes called “Theia”). This giant impact would change the course of our planet.
After being crushed by Thea, the Earth’s interior melted into chaos. The environment that was once the proto-Earth has completely changed, with almost all matter evaporating. There is a silver lining to this violent chapter in Earth’s history — we have the giant impact to thank for unleashing the debris that will become it the moon.
Read more: The origins of water on Earth may not have begun with an asteroid impact
Chemical residue from Proto-Earth
The ground was hard after the giant impact, but its surface eventually cooled and hardened. The materials from Proto Earth seem to have disappeared forever.
However, the new study seems to prove that this is not true. When researchers examined samples of rocks in Greenland and Canada, as well as lava deposits in Hawaii that originated from the mantle, they discovered an unusual imbalance in the isotope potassium 40.
Researchers had previously discovered a similar defect in meteorites that do not share Earth’s current composition. Hence the same anomalies in ancient rocks and lava deposits indicate that they contain materials that originated from the primordial Earth before Theia struck.
“This may be the first direct evidence that we have preserved Earth’s primordial materials,” author Nicole Nee, a professor of Earth and planetary sciences at MIT, said in her article. statement. “We’re seeing a piece of very ancient Earth, even before the giant impact. This is amazing because we expect this early signature to be slowly erased by Earth’s evolution.”
Meteor simulation
When testing rock and lava samples, researchers noticed a specific lack of potassium isotope 40, a feature that made these materials stand out compared to everything else found on Earth.
If the proto-Earth was indeed made of K-40-deficient materials, these materials would have undergone chemical changes as a result of meteorite impacts (including a giant impact). Given this assumption, the researchers used data from every known meteorite and tested simulations of meteorite impacts on early Earth. The simulations found compositions that are compatible with most modern materials found on Earth.
This reinforces the fact that ancient rock and lava samples somehow held on to the remains of the primordial Earth while everything around them changed after the giant impact.
However, no meteorites have been shown to share the same deficient potassium isotopes as these Proto Earth samples. Therefore, there may still be more evidence pointing to Proto Earth.
“Scientists are trying to understand the original chemical composition of Earth by combining the compositions of different groups of meteorites,” Ni said. “But our study shows that the current inventory of meteorites is not complete, and there is a lot to learn about where our planet came from.”
Read more: The Earth formed 4.54 billion years ago – how do scientists know this?
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