Perhaps you have heard a "crazy" theory that claims that we are descendants of aliens. As it turns out, in a way, this idea could be true.
Not that we were raised by little green men like those who usually appear in science fiction films, no.
But a study by Rice University in Texas, United States, published this week by the scientific journal Advances in science, stresses that a planetary collision occurred 4.4 billion of years brought to our planet the fundamental elements for the emergence of life.
"Our study indicates that the Earth has acquired its share of essential elements for life at a very late stage of its creation, possibly through the same impact that formed the Moon"geologist and scientist Damanveer Grewal told BBC News Brazil.
In astrophysics, addition is the name given to the accumulation of material on the surface of a star by the action of gravity.
"As the Earth has a long history of growth, spaced by accumulations of millions of years, gigantic impacts must have played an important role in the origin of life on our planet," said the expert.
"Key Elements for Life"
In an interview with BBC News Brazil, geologist and planetary scientist Rajdeep Dasgupta recalled that "carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus are the key elements to life as we know it."
"Without carbon, nitrogen and sulfur it is not possible to produce the hydrocarbons, amino acids and proteins necessary for life, so we focus on the origin of some of these fundamental elements," he explained.
"We can not rule out the possibility that the Earth has acquired its necessary dose of essential elements for life without having suffered episodes of gigantic impacts, yet the accessible carbon, nitrogen and sulfur inventory on our planet points to its source through a gigantic impact, as suggested in our study. "
According to the researchers, thanks to the study of primitive meteorites, it has long been known that rocky planets like Earth had, in their origin, scarce volatile materials.
"The timing and mechanism that led Earth to acquire such elements provokes enthusiastic debates," Dasgupta says.
"Our hypothesis may explain this phenomenon in a manner consistent with all the geochemical evidence"
The researchers compiled the results of a series of experiments conducted under high temperatures and pressure in a specialized laboratory at Rice University.
There simulated geochemical reactions this must have happened on Earth billions of years ago.
They started with an existing theory that argues that Earth's volatile compounds originated from a collision with a planet whose core was rich in sulfur – which is known as a "donor planet."
"Our main challenge was to explain why the surface of the Earth has a carbon-nitrogen ratio clearly superior to that of primitive meteorites," says Grewal.
"Our experiments have shown that if the core of a rocky planet is rich in sulfur, then the carbon is expelled to it at a rate higher than nitrogen."
Through these simulations, the scientists concluded that for this to happen this "donor planet" would have to be the approximate size of Mars.
That is, it would have been a gigantic collision. And everything indicates that it would be the same collision that formed the Moon.
The theory of great impact
The theory most accepted today by the scientific community to explain the formation of the Moon is the so-called high-impact hypothesis.
Presented in 1975 by researchers at the Planetary Science Institute of Tucson and the Harvard-Smithsonian Institute of Astrophysics, the theory states that 4.4 billion years ago a planet about the size of Mars, called Theia (or Tea), collided with Earth.
"Planetary impacts occur throughout the history of a solar system," explains Professor Dasgupta. "These impacts occur to this day, albeit with a much lower frequency, and the colliding planets are usually much smaller."
"Planetary impacts have been much more frequent in the first tens of millions of years of the history of the solar system," he adds.
At that time, the protoplanetary disk (a disc of material around a young star, where the formation of planets occurs) was still evolving and the orbits of several bodies were still being established.
The gigantic collision, which would have occurred at about 40,000 kilometers per hour, would not have been frontal but lateral.
It is believed that the poured much material, forming the Moon. Experts estimate that 90% of the lunar composition is originally from the ancient planet Theia.
The theory holds that the material that gave birth to the Moon stabilized about 22,000 kilometers from Earth, 27 hours after the collision (the current distance from Earth to the Moon today is 385,000 kilometers).
The rest of Theia would have been incorporated by Terra. And, according to scientists, this material would have brought the conditions for the emergence of life on our planet.
"The conclusion that the Earth's volatile body originated from a Mars-sized planet came from the combination of our experimental measurements, where we show how carbon and nitrogen can be separated from one another during the formation of a planet. with a core rich in sulfur, "says Professor Dasgupta.
"These simulations have proven that the greatest probability of getting carbon, nitrogen and sulfur is when the size of the collision body is that of a large planet."
To reach this conclusion, the scientists made computer models. They tested around 1,000 million scenarios conditions of the solar system.
"This is how we discovered all the isotopic signs of evidence, the relationship between carbon and nitrogen and the total amounts of carbon, nitrogen, and sulfur on Earth, consistent with the impact that formed the Moon: a Mars-sized planet with a rich core in sulfur, "says Grewal.
"This also explains why Earth and Moon are geochemically similar," Dasgupta concludes.
Life on other planets
The scientist says that understanding how life has formed on Earth can help in the investigation of similar phenomena on other planets.
"The study indicates that a rocky planet similar to Earth is more likely to acquire essential elements for life if it is formed and grow from gigantic impacts. with planets that have different elements in their composition, " comment
Undoubtedly, it is an interesting clue when it comes to pointing telescopes into space.