Worlds even more suited for life than Earth itself? Crazy to think about right?
In late 2020 the term "Superhabitable" exoplanets quickly filled the air of the Space community, as research published by astrobiologists at Washington State University found that in our search for extrasolar life, focusing on Earth- like planets may be narrowing our field for dicovery.
Scientist Dirk Schulze-Makuch argued that efforts should be focused on finding "Superhabitable" exoplanets, which may be a goldmine for extrasolar life to thrive on due to the habitat being more conducive for life than Earth itself.
Out of >4000 exoplanets, the research identified 24 possible "Superhabitable" worlds for future observation efforts.
Habitability is still a relatively new area of study. Every star has a 'habitable zone'. It has traditionally been suggested that this location is the best area to focus search efforts on for life.
However, as our understanding of our solar system develops, we have found that this is far from being the sole prerequisite.
~Traditionally known to be Earth's twin, Venus today is more like a distant relative from the world once known. Venus started out as a stable,water- covered eden, sharing the same habitability traits as early Earth. Around 700 to 750 million years ago, the geoclimatic nature of Venus shifted significantly. You could say the sun "scored" Venus to death, as a result of the runaway greenhouse effect the radiation from the sun became trapped by the thick atmosphere of Venus resulting in the hostile inferno environment of the planet today.
~Located within the habitable zone also, is the polar opposite to Venus. Uranus is too far away from the Sun, and therefore too cold to sustain life. Temperatures found in the lower atmosphere have been recorded at -223.8 Celsius ( -371 degrees F.)
The criteria for life extends beyond just being located in a stable habitable zone.
Requirements for a "Superhabitable" planet.
🌞Type of Star - Our planet is orbiting around a G-class star, the sun. Researchers have found that this may not be the best type of star to sustain life, as our sun has a lifespan of 5 billion years, however life as we know it will only survive with the conditions of our sun for 2 billion more years.
K- class stars are dimmer and cooler, yet have lifespans of 20-70 billion years. This is 5-8 times longer than G-class stars, and a massive advantage as it takes complex life 4 billion years to develop and evolve.
🌚 Moon - Important in stabilising the movement of the planet, particularly the axial tilt. The Earth has a relatively stable axial tilt, which oscillates between 22.1 and 24.5 degrees. On the more extreme end, Mars has an axial tilt which can reach as far as 60 degrees. This has an extremely dramatic impact on the climatic variations.
🪨Size - An ideal planet would be 10% larger and 1.5 times as massive as the Earth.
10%: Would allow for more surface area for life to develop.
1.5x: A core with more mass will result in the radioactive decay in the planets anterior decaying at a slower rate. This will maintain the atmosphere and retain the geothermal heat of the planet for longer. This is a really important factor, as researchers have estimated that even an increase of 5-8 degrees celsius in the temperature would lead to more variety in biodiversity and habitability.
🌎 Teceonics - The Carbon cycle process enabled by the movement of plate tectonic's helps to maintain global temperatures and sustains the strong magnetic field of the planet which prevents the atmosphere from being stripped away by solar winds.
🌦 Atmosphere - A planet with even 25% - 30% oxygen (with Nitrogen and other inert gases) will create a better living atmosphere compared to the 20% oxygen here on Earth.
These are some characteristics that which determine whether the planet has a "Superhabitable" environment.
The 24 identified "Superhabitable" exoplanets are only the start of our search!
Every week a new exoplanet is discovered, one out of every five sun-like stars has an earth-like planet. The argument that we are alone in this solar system is slowly becoming outdated the more we expand our search horizons. The James Webb and PLATO Telescopes, alongside the LUVIOR Optical Infrared Surveyor, are highly anticipated to be game changers in examining exoplanets and planetary atmospheres for habitability and signs of life.
The more that we disassociate from our conventional understanding of what life or the perfect planet looks like, the closer we may get to achieving the dream of finding life beyond Earth. Creativity and unconventionality thrive in Space research.