[RIA] Once upon a time, Earth was completely different, including in its chemical composition. But after a cosmic catastrophe, nothing remained—or so it was believed until recently. New discoveries are shedding light on the planet's history and the mystery of life's origin. However, not all scientists agree with the research findings.
"IT'S AMAZING."
Billions of years ago, the early Solar System was a rotating disk of gas and dust. From this chaos, the most ancient meteorites formed. Merging, they formed the proto-Earth and its neighboring planets.
It is believed that the early Earth was a rocky sphere covered in oceans of molten lava. But about four and a half billion years ago, it collided with another celestial body the size of Mars—this hypothetical planet is known as Theia. The mega-impact led to the formation of the Moon and completely remolded the interior of our world, changing its chemical composition.
It was believed that fragments of the primordial Earth were lost forever. However, a new discovery disproves this. Scientists from the Massachusetts Institute of Technology (MIT), along with colleagues from other research centers, have found traces of material from the "proto-Earth." The article was published in the journal Nature Geosciences."
The key to the discovery was a rare chemical "fingerprint"—a tiny but significant imbalance in the amount of potassium isotopes in very ancient rocks from Greenland, Canada, and Hawaii. They were found to have an unusual "deficiency" of the isotope potassium-40. This anomaly is unlike the composition of most modern terrestrial rocks and meteorites, indicating their different, more ancient origin.
Researchers believe the rocks discovered are surviving fragments of the primordial Earth, which somehow miraculously escaped complete mixing and remelting during a giant impact. Computer modeling has confirmed that if the proto-Earth initially consisted of such potassium-40-deficient material, then subsequent meteorite impacts and geological processes led to the formation of the composition we see everywhere today.
The chemical composition of these ancient rocks doesn't exactly match any known type of meteorite. This means that Earth's "building blocks" were unique, and scientists have yet to find their exact counterparts in space.
"This may be the first direct evidence that we've preserved materials from prehistoric Earth. It's astonishing," says Nicole Ni, an associate professor of Earth and planetary sciences at MIT.
Russian scientists highly value the quality of the work. "It was initially clear that some remnants of the 'original' Earth would be preserved in mantle rocks. However, quantitative estimates of a specific isotopic anomaly (K40), which allow us to estimate the material of the proto-Earth, have been obtained for the first time," explains Sergei Voropaev, PhD in Physics and Mathematics and a senior researcher at the Laboratory of Carbon Geochemistry at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences.
LIFE PROVIDER
Another recent study notes that without a collision with another planet, life would never have emerged. Scientists from Imperial College London suggest that Theia formed farther from the Sun. Low temperatures led to the condensation of volatiles such as hydrogen and carbon—essential elements for the formation of organic matter. On the hot early Earth, these elements would have evaporated. Thus, Theia became a cosmic "supplier of the ingredients necessary for the origin of life," explains study author Pascal Kruttach.
To prove this theory, specialists studied manganese and chromium isotopes in terrestrial rocks and meteorites. The radioactive decay of these elements acts like a precise clock, allowing us to peer into the first 15 million years of Earth's history. The analysis revealed that the volatiles on our planet are alien in origin and were delivered by a massive body from the outer solar system. The research paper was published in the journal Science Advances.
The work echoes other studies. For example, another simulation showed that Theia could have delivered a huge amount of water to Earth, which is still preserved in the deep mantle. This water did not have time to rise to the surface and form oceans, remaining sealed within the planet's interior since its formation.
WAS THERE A THEIA?
Although the Earth-Theia collision theory is the dominant theory in science, not all scientists share this idea. For example, an alternative view was proposed by Erik Galimov (1936-2020), former director of the Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI RAS). He also has followers among his colleagues.
"I believe that the embryos of the Earth and the Moon formed from a common, rarefied condensation and then grew due to the fall of bodies much smaller than Mars," says Sergei Ipatov, Doctor of Physical and Mathematical Sciences and leading researcher at the Laboratory of Thermodynamics and Mathematical Modeling of Natural Processes at the Russian Academy of Sciences' Geochemical Institute.
Commenting on the MIT study, he notes that the discovery of rock samples with an unusual potassium isotope composition can be explained without the mega-impact theory.
"In my calculations, the Earth's growth initially occurred due to matter formed near the Earth's current orbit. Then, bodies from various regions of the Solar System began to fall onto the growing nucleus. That is, even without a mega-impact, the Earth grew over time due to matter formed at different distances from the Sun. And the elements that formed the Earth's initial nucleus could have been different from those that appeared later," the scientist explains.
Moreover, Ipatov does not share the idea that life could not have originated without a collision with another planet.
"During the mega-impact, a significant amount of matter evaporated, which would not have been conducive to the emergence of life," he points out. "Water and volatiles could have been brought in by bodies coming from beyond the orbit of Mars."
Sergei Voropaev, in turn, adds that life appeared when suitable conditions arose.
"The magma ocean cooled, and the primordial crust formed and cooled sufficiently," the scientist explains. "The atmosphere poured down in a gigantic rain—water condensed, and oceans and seas formed. The proto-Earth played little role in this process; the basic elements—the building blocks of future life—were present in abundance in all variations. It was a combination of natural processes and phenomena, driven by the planet's distance from the Sun, energy flow, cyclicity, and other unique features."
Thus, the question of the fate of the early Earth, as well as the emergence of life on it, remains open. This means researchers still have much work to do.