When it comes time for the human civilization to leave the blue-green jewel now called home astrobiologists say humans must find a more perfect Earth to call home. Of course people may think – what make this Earth not perfect? Well, when it comes to the biosphere, they say Earth isn’t the best example. Astrobiologists believe that those searching for our next Earth should be looking for “superhabitable” worlds. Locating super Earths may sound like science fiction to some; however, astrobiologists now know where to look.
Previously, the way in which astrobiologists search for extraterrestrial life includes analyzing the habitable zones (HZ) of our galaxy and all around the observable universe. Astrobiologists are beginning to stem away from this notion, stating that it is possible to find life on the outside of these zones in orbiting moons and below the surfaces of exoplanets. One of the main prerequisites for a planet to be considered to be in an HZ is the presence of liquid water. However, astrobiologists have found that even with the presence of liquid water, life is unable to flourish because of other extenuating factors, such as atmospheric pressure, lack of magnetic shielding, and a less than optimal land-to-ocean-fraction and distribution.
This new prerequisite for potential planets is met with some skepticism. Creator of the circumstellar habitable zone theory, Jim Kasting, stated, “a planet is either habitable or not.” Other scientists agree that if liquid water exists on a planet then it is well within the stellar borders of extreme temperature and at a safe distance from its star.
Ravi Kopparapu, Penn State University physicist, stated that he is in favor of Heller and Armstrong’s concept and opposes the restrictive nature of habitable zone theory. Many exoplanets found within the HZ have been determined unfit for life. The Heller-Armstrong concept proves that worlds outside of the HZ have the potential to harbor life – most notably the moons of Saturn and Jupiter. These moons have vast underground oceans where liquid water is able to exist. Considering that Saturn and Jupiter fall outside the zone which was previously deemed the only place fit for life, worlds like these deserve another look. With the numerous exoplanets that have been found outside the HZ, this new concept may help astrobiologists locate a more perfect earth.
Astrobiologists are using Earth as the comparable. If a world like this one can foster life, even a nuclear-powered, space-faring species, for billions of years then it ought to a fair starting point; though it is appearing that astrobiologists are searching for a planet that will look much different than the current one.
One of the main prerequisites for a new Earth is that it will be at least two to three times larger than this planet. Astrobiologists René Heller and John Armstrong wrote a paper describing over 18 factors that will determine a potential new home is suitable for the human race. Heller and Armstrong also state that the ideal planet will be orbiting a star that is smaller and older than the sun. New host stars that will fit the new mold will most likely be K dwarfs. K dwarf host stars have a surface temperature less than the sun. Unlike the sun, they burn hydrogen at a slower, more efficient, rate that allows them to burn at a constant rate for longer.
Like the Earth, the planet should also have been exposed to outside object that crashed and pummeled it in the past. With this it will have been exposed to organic molecules and catalysts to create a basis of life that will evolve into a planetary environment. Even though Earth orbits around a host star in a stable manner, remarkably, scientists state that this is not a necessary requirement.
Astrobiologists already know where to look for superhabitable planets because they believe they have already found one. Both Heller and Armstrong believe that the star Alpha Centuri B is the closet match – 4.37 light years away. The star hosts a planet that is similar in size to Earth orbiting the star at 3.235 days. Its sun is also more developed than the center of this solar system, and shows signs of subdued radiation.
In 2018, NASA plans to launch the James Webb Space Telescope, which will enable astrobiologists to see further into space with greater resolution. This telescope will allow them to determine the atmospheric makeup, chemical composition, and liquid water density of a potential home away from home. Such advances in technology will undoubted help astrobiologists in their quest in finding a more perfect Earth.
By: Alex Lemieux