NASA
How did the earth, alone among the rocky planets of the solar system, become the home of life? How, between both cold and absence of life, has our planet become hot, welcoming and capable of sustaining life?
The answer to these questions is complex and multifaceted, and part of it comes from cosmochemical – An interdisciplinary field that studies how the chemical elements are distributed in the universe.
The solar system is a place in constant motionit was even more chaotic 4.5 billion years agowith the planets still in formation and plansimals and planetary embryos moving rapidly and colliding with each other.
Somehow, in the middle of all chaos, the earth received more than its part of carbonáce condritos – And with them amino acids and other chemical compounds essential to life.
According to cosmochemical studies, they demonstrated that between 5% and 10% of Earth mass It will have come from carbonated condominiums that collided with the planet still young. And a significant part of this was brought by the Impact Theia, which formed the moon.
To test these ideas more rigorously, three researchers used dynamic simulations of solar system formation to try to reproduce this scenario.
The study calls itself “Dynamical origin oh Theia, the last giant impactor on Earth“. The main author is White Duartefrom the Institute of Astrophysics and Space Sciences, at the Lisbon Astronomical Observatory, Portugal. The investigation will be published in the Icarus Magazine.
One of the fundamental distinctions in cosmochemistry is between carbonaceous condominiums and non-carbonaceous meteorites. This distinction Divide the solar system meteorites into two groups And suggests that there are two distinct reservoirs of material in the solar system.
The CCs formed farther from the sun, probably beyond Jupiter, and carry more volatile compounds such as water and volatile compounds such as water and organic compounds. NCs include, for example, metallic meteorites, and contain less volatile.
To test the hypothesis that Theia will have brought CCs and volatile compounds to Earth, the investigators performed detailed simulations of the solar system -Simulations n-bodies of the final phases of the growth of rock planets.
The simulations included CCs that were diverted into the solar system, while Jupiter and Saturn were still growing and accumulating matter. Due to the size difference between Planeta e planetary embryosEmbryos were more likely to interact with the land planets and give them CC material.
An obvious result was that the instability of the giant planets – especially the change of orbit of Jupiter – had a striking in the way the earth accumulated CC material.
An obvious result was that the instability of giant planets – Especially the change of orbit of Jupiter – had a remarkable effect in the way the earth accumulated CC material.
The researchers performed three types of simulations: the first was only small, with platesimal CC; The second were only large, with CC planetary embryos; and mixed, with both types of CC.
For one subset of 10 simulations of each scenarioadded the effect of the dynamic instability of the giant planets – known as the Nice Model in Astronomy – which describes how the giant planets altered their orbits after graduating.
The goal was to understand how CCs and NCs were distributed in the solar system and why the land eventually received more CCs than the other rocky planets, especially Mars. They also intended to understand if the impact with Theia could be responsible for much of the Earth’s CC material.
When researchers included the dynamic instability of the giant planets, the Results became even more interesting. “The instability of the giant planets drastically altered the evolution of the system, causing a strong increase in eccentricity of the orbits, which resulted in a vacancy of collisions and ejections,” the authors wrote.
However, the Final state of the system did not change much.
One key point of simulations is the impactor Theia. Previous study suggest that Theia may have been a carbonaceous body. If this is true, a significant part of Earth’s habitability may have resulted from this impact.
“In the mixed scenario, without instability of the giant planets, the final impact of the Earth had a CC component in more than half of the simulations. In 38.5% of simulations, the final impact was a pure CC embryo, and by 13.5%, the impactor was an NC embryo that had previously absorbed a CC embryo,” the researchers explain.
Overall, simulations show a Primitive solar system with two distinct rings of plansimal: a inner ring of rocky plansimal e um anel exterior of the carbonacy.
Later, as the gaseous giants migrated inside, they boosted CC material to the inner solar system. Some of these were trapped in the asteroid belt, while others – more massive – were thrown into the orbits of the rocky planets.
“The final phase of ground planets has involved a number of giant impacts between NC embryos and platesimal, with occasional impacts of CC objects,” the authors explain.
This scenario helps to explain various characteristics of the solar system: the masses and orbits of the terrestrial planets, the orbital distribution of asteroids and also the proportion of CCs on Earth and Mars – Mars does not have the same abundance of CC material as the earth.
If only the plansimals (and not embryos) brought CCs, as in the scenario “only small”, then Mars and Earth would have similar proportions of CCs – which does not correspond to reality.
The investigators wanted to show that Theia could have been the last major impact on Earth and carrying large amounts of CC material-and seem to have achieved it.
The study shows that the last impact occurred between 5 and 150 million years After the dispersion of the gas. Most of them took place between 20 and 70 million years. Despite uncertainties about the exact moment of impact with Theia, the results are compatible with existing estimates.
Simulations also confirm that embryos and platesimal CC may have been incorporated throughout the earth’s growth, but that they were especially relevant in the early stages.
“In the context of this scenario, the last giant Earth impactor contained a CC component in about half of the mixed simulations,” write the authors.
“In most of these cases (38% of simulations), Theia was a pure CC embryo. In the remaining cases, Theia was an NC embryo that had previously accumulated a CC embryo.”
The investigation also highlights the Importance of Jupiter in the structure of the solar system. Not only limits the asteroid belt, but it was also fundamental to determine the final composition of the terrestrial planets – by launching CC material from the outside to the area where rocky planets were formed, especially the earth.
Millions of factors had to occur perfectly so that the earth would become the habitable world we know. We do not know how likely it is that there are other similar worlds. It may be that being in the habitable zone is not enough – perhaps a giant planet with Jupiter is also necessary to push carbon and volatile compounds for rocky planets.
In the simulations, the final impact of the earth was with Theia – and this body had high concentrations of CC material, which helped make the earth habitable. This result is in accordance with the current scientific thinking.
Teresa Oliveira Campos, Zap //
