Life on Earth appeared more than once: what scientists say
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A Portuguese astrobiologist suggests that for the first time, life on the planet could appear several times, and in different places.
Now scientists are intensively looking for life on other planets, but how life on Earth originated is still known very little. Portuguese astrobiologist Zita Martins, who is researching both issues, suggests that life on Earth could have originated several times, and at the same time in several places on the planet at once, Forbes writes.
“There is still no exact understanding of how exactly life appeared on Earth. We have some data on the chemical processes that preceded its appearance. We also know a lot about the physical and geological processes on the planet when the solar system was just emerging. But how did the process of the emergence of life happen? We still have to work on this, “says Zita Martins from the Institute of Technology Lisbon, Portugal.
Scientists believe that life on Earth could appear within the first 200 million years after the formation of the planet (and it is known to be about 4.5 billion years old). But so far, scientists have discovered the oldest evidence of life, which dates back to a period of 3.5 billion years.
How could life appear on Earth?
Many of the organic molecules that make up cellular life can be found in meteorites, asteroids and comets, Martins says. These molecules just delivered these space objects to Earth in the early history of the planet. Martins believes that the impact events that accompanied the fall of these objects could also contribute to the emergence of life in certain, separate places on Earth.
“With my colleagues, we created a model of a comet's fall to Earth. As a result of such an impact, a huge amount of energy, and we came to the conclusion that this energy from the impact could provoke the breaking of molecular bonds and thanks to this, more complex molecules appeared, “says Martins.
According to the scientist, at the moment when the Earth cooled down (and at first it was a hot ball), and water appeared on it, conditions appeared for the emergence of life. But it is quite possible that microbial life could have evolved in many places around the same time.
“In order to understand what were the original molecules that became the basis for the emergence of life on Earth, it is important to know the early chemical composition nebulae from which the solar system was formed, and we constantly find a diverse molecular composition in the meteorites, comets and asteroids that witnessed the birth of this system, “says Martins.
The composition of the gas and dust that formed our solar system is also important in understanding what type of interstellar chemistry formed the first chemical building blocks of our early solar system.
Why is it that only certain conditions are needed for life to appear?
“Why is it that only certain molecules are needed for life to emerge? This question may never be answered. We can only speculate. In addition, we lack an understanding of how life made the big leap from just prebiotic chemistry (i.e., the processes before its appearance) to actual biology. But you need to try to find out what types of molecules were available in the distant past from which life could begin,” says Martins.
According to Martins, the most important questions :
- When exactly did life appear on Earth?
- Why did it appear on our planet?
- Was there some event that was the real catalyst for the origin of life on Earth?
“I am particularly interested to know if similar conditions that occurred during the origin of life on Earth were in other places in our solar system,” says Martins.
Life on Earth originated more than once?
“I'm not entirely sure that we will ever be able to know for sure , in what period of time life appeared on Earth. But I am sure that we can learn about the conditions that were in the solar system shortly before the origin of life on Earth, “says Martins.
According to the scientist , we are trying to detect life on other planets, but it is still difficult to define exactly what life is. The simplest definition would be the following: it is a self-sufficient system that has the ability to replicate (the process of creating new molecules from the parent molecule). But there must also be a metabolism.
Focus already wrote that scientists, as a result of research this year, came to the conclusion that microbial life already existed on Earth after 300 million years after the formation of the planet.