Over the past two decades, humanity has discovered more than four thousand exoplanets outside our solar system. Some of these already discovered objects may well support life, according to the portal phys.org. In order to draw conclusions about which planets can give hope for humanity in its eternal quest to find “brothers in mind”, a unique supercomputer NASA Discover was created, which simultaneously predicts the future climate of the Earth. So how exactly can terrestrial climate models help in the search for alien life?
What could be the climate on exoplanets?
As you know, the most promising planet for studying for habitability is the one that supports a number of necessary conditions at once. So, the found world should be rocky, have liquid water on its surface, maintain the atmosphere and possess a magnetic field that would protect local life from the cosmic wind. Despite the fact that modern technologies do not allow us to study distant exoplanets orbiting alien stars with detailed accuracy, and the spacecraft's journey to the nearest one would take 75 thousand years, researchers can now judge the climate of distant worlds based on the planet that has become our home is the Earth.
Such a variant of studying distant worlds became possible for realizing the so-called "transit method", which helps not only when searching for exoplanets, but also when analyzing their distances to parent stars to estimate the percentage of light blocked by planets. Such indirect data help experts to judge the mass of the exoplanet and its approximate climatic characteristics. However, no matter how we try to compare objects found in distant space, many of them are so different from Earth that they seem to be taken from the imagination. Thus, most of the planets discovered by NASA's Kepler space telescope do not exist in our solar system.
Most often, the exoplanets found are located between the size of the Earth and the gaseous Uranus, which is four times the size of our planet. In addition, the vast majority of potentially habitable exoplanets are located near dim stars - red dwarfs, which make up the vast majority of stars in our galaxy. Due to the small size of red dwarfs or M stars, planets should be located a short distance from their bright red star - closer than Mercury to the Sun. Such an inconvenient fact makes scientists argue about the possibility of habitability of such worlds, because it is known that, despite their small size, red dwarfs are very hot-tempered, splashing out 500 times more harmful ultraviolet radiation than our Sun does. According to experts, such an environment could almost instantly evaporate all oceans, deprive the atmosphere and fry any DNA on a planet close to a red dwarf.
Climate on the exoplanet closest to Earth
Earth's climate models show that rocky exoplanets around red dwarfs can be habitable even with radiation. For example, a team from NASA recently simulated possible climatic conditions on Proxima B, also located next to a red dwarf star, in order to test if there is a possibility of a warm and humid climate, so important for organic life.
Proxima B is a potential candidate for detecting alien life
Proxima B orbits the star Proxima Centauri in a three-star system located just 4.2 light years from the Sun. Scientists believe that the world they discovered is rocky, based on the estimated mass of the planet, which is only slightly larger than Earth. The main problem with Proxima Centauri is that it is located 20 times closer to its star than the Earth is to the Sun. Thus, it takes an exoplanet only 11.2 days to complete a revolution around its star. Such an inconvenient location could turn Proxima Centauri B into a gravitationally blocked world, which does not bode well for life on such a planet.
The team of Anthony del Genio, a NASA planetary scientist, was able to modernize the Earth's climate model, first developed in the 1970s, in order to create a planetary simulator called ROCKE-3D based on the aforementioned NASA Discover supercomputer. The results of an unusual experiment showed that modeling greenhouse gases and water in the atmosphere of Proxima B makes it possible to judge the presence of clouds on the exoplanet, acting by analogy with an umbrella and reflecting the harmful radiation of the parent star. The presence of such a phenomenon could lower the temperature on the sunny side of Proxima b from hot to warm. Other scientists have discovered that Proxima can form clouds so massive that they would eclipse the entire sky if viewed from the surface.
Proxima Centauri's surface may be obscured by massive clouds
A similar unusual phenomenon can occur if the planet is gravitationally closed and slowly rotates around its axis. A force known to mankind as the Coriolis effect causes convection where the star heats up the atmosphere. In addition, the combination of the atmosphere and the circulation of a possible ocean on the planet's surface could move warm air to the night side of this alien world, which in turn will protect the planet's atmosphere from freezing, even if part of the planet is deprived of any light.
Despite the fact that scientists are currently deprived of the opportunity to test their theoretical knowledge, the researchers hope that the launch of the James Webb Space Telescope will help confirm or disprove their hypotheses about the climate of the nearest exoplanet.