To date, astronomers have discovered a sufficient number of various planets in the Universe - from hot worlds with a hot surface to cold frozen ice balls.
While the search for planets similar in their characteristics to our Earth continues, new studies prove that life can exist in conditions significantly different from those on Earth.
“When we talk about habitable planets, we mean worlds where liquid water exists,” says Stephen Caine, a scientist at NASA's Exoplanet Science Institute at the California Institute of Technology in Pasadena. "The planet should be at a distance from its sun, where it is not too hot and not too cold." This area is called the "habitable zone " (habitable zone) and depends on the size and type of star.
But not all exoplanets revolve in Earth-like orbits, that is, at a constant distance from their stars. Scientists have found that many planets have highly elongated elliptical orbits, and spend only part of their path in the habitable zone. They are cold worlds that heat up for a short time between long cold winters.
Although the conditions on such planets are very different from those on Earth, there is still a possibility that life may exist on them. On Earth, scientists have discovered tiny life forms that can survive in extreme conditions (very high or low temperatures, excessive pressure, etc.). They are called extremophiles. Some organisms can slow down their metabolism to zero in order to survive prolonged cold conditions. Others are able to survive in extreme heat conditions if there is a protective layer of water or soil around them. Studies were carried out, during which it turned out that earthly spores, bacteria and lichens are able to survive in the extreme conditions of the Earth and space.
Scientists suggest that the habitable zone around the star may be larger than previously thought. And planets where living conditions are hostile to humans can be ideal habitats for extremophiles such as bacteria and lichens. Indeed, on our Earth, life in the early stages developed in much harsher conditions than now.
The researchers note that suitable conditions for life can exist not only on the exoplanets themselves, but also on the satellites of large gas giants like our Jupiter. Satellites of planets that are permanently or spend some time in the habitable zone may also be habitable.
Take Titan, Saturn's largest moon, as an example. It has a dense atmosphere, but it is located quite far from the Sun and is too cold for life to exist on its surface. However, if it were possible to move Titan closer to the Sun, then terrestrial instruments could detect enough water on it and suitable conditions for life.
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However, so far, scientists cannot accurately determine the presence of suitable conditions for life on already discovered exoplanets, since they do not have enough data on their atmospheres.
However, research results show that life in the universe can exist in a wide variety of forms, and not only on planets similar to our own. And scientists at the Institute for Exoplanet Research are continuing to work to determine which of the planets already discovered may be suitable for extremophile life, or be habitable satellites.