Scientists may have to revise its estimate of the number of planets outside the Solar system that can be inhabited. In the new study, experts from University of California at riverside reported that the presence of toxic gases in the atmospheres of most planets makes them unsuitable for complex life as we know it. On their findings the researchers divided the article in the journal The Astrophysical Journal. Press release research published by the website Phys.org.
How to search for habitable exoplanets?
Traditionally based part of the search for extraterrestrial civilizations has focused on what astronomers are called the “habitable zone”, which is defined as the range of distances from a star within which the surface of the planets could theoretically exist water in liquid form. However, this condition will only be true for basic single-celled microbes, but not for complex life forms such as animals, the Kingdom which include many types, ranging from simple sponges and ending with man.
Article scientists published in The Astrophysical Journal, shows that the projected levels of certain toxic gases reduces this is safe for the existence of complex life zone, at least twice, and in some cases completely eliminates it.
“We first used the calculations of the physiological limits of life on Earth to predict the probability distribution of complex life forms elsewhere in the Universe,” explains one of the study’s authors, Timothy Lyons.
“Imagine a safe for complex life forms a habitable zone capable of supporting the existence of rich ecosystems like the earth. Our results show that complex ecosystems like ours, can not exist in most parts of the habitable zone, as previously thought,” he added.
Using computer modeling to study atmospheric photochemistry, and climate on different planets, the researchers looked at a feature of such a gas as carbon dioxide. Any scuba diver knows that the presence of too large amounts of the gas in the body can kill. However, planets that are too far away from its star, need carbon dioxide because it creates the greenhouse effect needed to maintain their surface temperature above zero. Just as on Earth.
“That water could be present in liquid form on the surface of the planet, on the edge of the conventional habitable zone, this planet will need to have tens of thousands of times more carbon dioxide than is available today on the Earth. And, as we know, far above levels deemed toxic to humans and overall animal life on Earth,” says Edward Smitherman, the lead author of a new study.
In the new study, researchers found that the toxicity of carbon dioxide limits the life of simple organisms half of the traditional habitable zone. For humans and other more complex animals, the safe area is reduced to less than one-third of this area.
Moreover, for some stars, generally there is no safe zone. These include two nearest neighbor of the Sun is Proxima Centauri, and TRAPPIST-1. The type and intensity of ultraviolet radiation, which emit these cool, faint stars, can lead to high concentrations of carbon monoxide (carbon monoxide), another deadly gas. It binds to the hemoglobin in animal blood, which transportorul oxygen through the body. Even a small amount can lead to death of body cells due to lack of oxygen.
Carbon monoxide cannot accumulate on the Ground as a hot and bright Sun causes a chemical reaction in the atmosphere, which rapidly destroy it. Despite the fact that a group of researchers recently came to the conclusion that the microbial biosphere can thrive in and on the planet with excess carbon monoxide, Smitherman emphasizes that “it’s definitely not a good place to live people or animals, at least similar to those that they oppress on Earth.”
In the Universe where life is possible?
To date, astronomers confirmed the discovery of almost 4,000 planets orbiting other stars. But not one of them we will not be able to attend. They’re just too far away. The nearest to us is Proxima Centauri b. To her to fly, using available technology, need 54 400 years. So at the moment the only way to study exoplanets remain telescopes, which can detect the presence of different gases in their atmospheres.
“Our discoveries give us the opportunity to decide which of these innumerable planets, we need to examine in more detail,” says Christopher Reinhard, another co-author of the study.
Previous studies of this group of scholars have formed the basis for the development of new space telescopes that will be able to more effectively search for extraterrestrial life.
At the same time, all modern attempts to detect extraterrestrial life prove just how rare and special our planet is. According to Smitherman if extraterrestrial life somewhere in the Universe exists, then surely it’s hidden deep beneath the surface of the planets.
“As far as we know, Earth is the only planet in the universe that can support complex life on its surface”, — concluded Smitherman.
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