Our only sample to assess the suitability of exoplanets for life is the only planet in the entire cosmos: Earth. Our home planet is the only one on which we know for sure that life originated.
However, the form of life known to us may not be limited to Earth-like planets; Indeed, scientists have recently identified the type of exoplanets that may have been favorable for life for billions of years.
The main thing is liquid water, which is present there for a long time. Here on earth, liquid water was crucial to the emergence of life. Exoplanets that may be able to retain liquid water may also have a better chance of life emerging.
According to a new study led by astronomer Marie Mol Loose at the University of Zurich, a thick atmosphere of hydrogen and helium can indeed maintain life-friendly temperatures and environmental conditions for long periods of time.
“One of the reasons why water on Earth is liquid is the atmosphere. “Thanks to its natural greenhouse effect, it can capture just the right amount of heat and create an environment conducive to the oceans, rivers and rain,” said Ravit Eled, an astrophysicist at the University of Zurich.
However, the Earth’s atmosphere was not always what it is today. It now contains mostly nitrogen, followed by oxygen and containing only a small amount of hydrogen and helium.
When the planet was newly formed, it had a so-called The first atmosphere, which consisted mainly of hydrogen and helium: the main constituents of the dust and gas cloud from which the sun and its system formed.
The Earth lost its primary atmosphere at a fairly early stage, and this was probably due to several processes; Including radiation from very hot, young sun and meteorite bombardment.
But it is possible that a super-Earth-type exoplanet – more massive than Earth but less massive than Neptune – could maintain its original atmosphere for much longer than Earth could.
“The greenhouse effect could have such a massive atmosphere for the first time, like the current atmosphere on Earth. Therefore, we wanted to find out whether such an atmosphere could create the necessary environmental conditions for liquid water, “- said Eled.
For such research, the group applied simulations; Modeled exoplanets that had nuclei of different masses, atmospheres, and distances from their own star. The researchers considered only sun-like stars.
The results showed that exoplanets with thick primary atmospheres could indeed be warm enough to hold liquid water for even a maximum of 10 billion years.
However, there are some moments. To prevent stellar radiation, which can destroy the primary atmosphere, the exoplanet needs to be far enough away from the star – about twice as far away from the earth as the sun. In the solar system it is so far from the sun that water would freeze on the surface of the planet.
But the sun is not the only source of heat for the planet. Some planets, including Earth, can generate their own heat. There are several ways to do this, including geothermal processes and the presence of radioactive elements that emit heat during decay.
Consequently, if a super-Earth-type exoplanet at such a distance from the parent star has a primary atmosphere and a sufficient amount of internal heating, a favorable environment may be created to retain liquid water on the surface.
“It may come as a surprise to many. “Astronomers typically suggest the presence of liquid water in regions around the star that receive adequate levels of radiation: not too much for the water to evaporate and not too little for it to freeze completely,” said Christoph Mordasin, an astrophysicist at the University of Bern.
According to him, since the existence of liquid water is probably a necessary precondition for life, and life took millions of years to emerge on Earth, this could greatly expand the horizon of the search for extraterrestrial life forms. The astrophysicist also says that according to their research, life can arise e. წ. Also on wandering planets that do not move around any of the stars and float freely in the galaxy.
According to this model of internal heating, life should hypothetically be possible on planetary bodies with thick ice sheets, such as Saturn’s moon Enceladus and Jupiter’s moon Europa, as well as satellites of planets orbiting the galaxy.
The group model requires the presence of many different details at exactly the right place and time. This is not impossible at all – if we give up everything, there is an earth and life blooms on it. However, this may not easily happen.
“While our results are exciting, they are probably still a drop in the ocean. In order for such planets to have liquid water for a long time, they must have exactly the right amount of atmosphere. “We do not know how common this is,” Mordasin said.
Even in suitable environmental conditions, as he points out, it is unknown how much life has a chance to emerge in such an exotic habitat. This is already a matter of astrobiology, but this study still shows that our Earth-centric view of life-friendly planets is very narrow.