The history of our planet as we know it may have begun with the collision of two early planets of our solar system, Gaia and Theia. It is thanks to this impact that we have the Moon, and we could thank this impact for another basic characteristic of our Earth: plate tectonics.
Shock and movement. Through geodynamic models, a group of researchers from the California Institute of Technology (CalTech) concluded that the collision between Gaia and Theia, which would have given rise to the modern Earth and Moon, was decisive for our planet, which is some day old today. dynamic tectonic plates.
“Submerged Continents”.The study is based on the so-called large low-velocity provinces (LLVP). These are two large masses of rock located at the bottom of the earth’s mantle, discovered in the 1980s.
These masses have geochemical properties that distinguish them from the rest of the Earth’s mantle. They get their name from this fact, as seismic waves slow down compared to the rest of the mantle as they pass through them.
A study published a few months ago showed that these large masses were possible remnants of Gaia, a planet that collided with the “proto-Earth” (Theia or Thea). Some of the matter released after the impact would eventually come together gravitationally and give the shape of the Moon. The remains of Gaia would end up being “eaten” on Earth by them.
geodynamics The new study is based on this hypothesis. The team drew on this event to formulate their geodynamic models and create a simulation of what happened. The team used the information we have about the composition of LLVPs to also understand how they affect thermal circulation in the Earth’s mantle.
They concluded that by cracking the planet’s surface, the impact may have enabled a sequence of subduction movements between the various plates that “float” on the Earth’s mantle.
Zirconium crystal. The team points out that this hypothesis could explain the oldest minerals on Earth, zirconium crystals. As they explain, these features would have been formed by these subduction movements more than 4,000 million years ago.
Details of the study were recently published in a journal article Geophysical Research Letters.
A science yet to be established. The fact that this work was formulated on the basis of a hypothesis that has not yet been proven limits our ability to conclude the matter.
Getting into the first hundreds of millions of years of our planet is extremely difficult. The geological record is very limited in these cases. If we exclude meteorites, rocks that did not originate on our planet, the oldest samples we have are around 4 billion years old.
It’s one of the reasons why extraterrestrial samples, like the Bennu or lunar regolith samples we bring back from our satellite, are so important. Although what we want to understand is our planet.
In Xataka | The moon is 40 million years older than we thought. We know this because of some old samples
Image | Simulation of impact effects. NASA Ames Research Center
