The collision that gave us life: what would have happened if Theia had never collided with Earth

Before the seas, rains or any form of life existed, the Tierra it was just one rock sphere that rotated under an incandescent Sun. It was missing everything: water, atmosphere and time. Just one unlikely collisionoccurred ago 4.5 billion yearschanged his destiny forever.

According to a new research from the University of Bernpublished in Science Advancesour planet was born dry, without the essential compounds for life. It was the impact with Theiaa body of size of Martewhich provided the water, carbon and sulfur that made a habitable world possible.

The study, led by scientists Pascal M. Kruttasch and Klaus Mezger, suggests that Without that collision the Earth would have remained an arid rock. A planet without oceans, without atmosphere and, probably, without history.

The Earth that was born too soon

Swiss scientists reconstructed the first chapters of Earth’s history by analyzing the chemistry of meteorites and mantle rocks. Their goal was to understand how the planet formed and why it lost the compounds necessary for life. The answer was as clear as it was unexpected: the Earth formed too quickly.

According to the study, the planet completed its chemical composition in less than three million years from the birth of the solar systeman extremely short period in cosmic terms. At that time, temperatures were so high that volatile elements – such as hydrogen, carbon or sulfur – could not be incorporated into solid materials.

Thus, the proto-Earth was consolidated as a sphere of dry rock, without water or gasesvery different from the bodies most distant from the Sun, such as comets or icy moons, which were able to preserve them. In the words of the authors: “Proto-Earth was initially a dry, rocky planet”, condemned to sterility until cosmic chance intervened.

Before, planet Earth was a sphere of dry rock, without water or gases.

The atomic clock that revealed the origin of the planet

To precisely determine that origin, the team used a dating system based on the radioactive decay of manganese-53 to chromium-53. This method acts as an atomic clock of planetary formation, since its half-life 3.8 million years It allows us to calculate exactly when the materials that shaped the Earth differentiated.

The result was overwhelming: the materials that would form the planet stopped interacting with the gas of the solar disk a few years ago. three million years. At that point, the Earth already had a core, mantle and crust in formation, but it was still a dry body without an atmosphere.

This data also coincides with the disappearance of gas from the protoplanetary diskwhich reduced to a minimum the possibility of incorporating new volatile elements. In summary, The Earth was born before its time, when the solar environment was not yet ready to create worlds with water.

A representation of Theia, the planet that collided with Earth. Photo: AI (ChatGPT)

Theia’s role: a collision that changed everything

If the Earth was born dry, where did the water that covers more than 70% of its surface come from? The answer is in Theia. This planet, formed further from the Sun, did contain water and volatile compounds. When it collided with the early Earth, it brought those elements and changed the history of the planet forever.

The impact was so violent that it melted large portions of rock and mixed the materials of both worlds. The simulations indicate that the earth actual is composed of a 90% from original material and 10% from Theia. That small fraction was enough to transform an arid planet into a fertile one.

As the study points out, “the Earth does not owe its habitable character to continuous evolution, but to a chance event: the late impact of a water-rich foreign body.”