By: Jerry Zhang
As humanity expands beyond the confines of Earth, people will begin traveling to planets deemed “hospitable” by scientists. But what do these planets look like? The simple answer is that they resemble Earth.
Earth is the only known planet with life, and it provides everything humanity needs to survive. When considering potential planets for habitation, they need to be similar to Earth in terms of natural resources, atmosphere, size, distance from the sun, and other factors for humans to live on them.
The planet’s star is a significant part of the discussion. If the star emits high levels of ultraviolet radiation, which causes skin cancer, it would likely be an inhospitable place to live. Furthermore, if the star has high light variation, it could cause dramatic effects on the temperature and weather of the potential planet, making it less stable for long-term habitation. Therefore, we would need to first find a star that meets these conditions, which accounts for around 5% to 10% of the stars in the Milky Way.
A planet’s makeup is another critical factor in selecting a planet for human habitation. It would need to be large enough and dense enough to have a gravitational field capable of supporting an atmosphere to protect from UV radiation. Additionally, water is crucial for sustaining human life. Without it, people would struggle to stay alive. Apart from water, the planet would also need to possess oxygen, hydrogen, nitrogen, carbon, and their simple compounds.
The planet’s orbit plays a part in its habitability as well. The planet should have a stable orbit within the habitable zone. Too close to its star, and the planet would burn up; too far, and it would freeze. The planet would also need to not have a large tilt, or else the seasons would become too extreme for any life to survive. On top of that, the planet needs to rotate quickly enough to produce a magnetic field.
Some potentially habitable planets include Gliese 667 Cc, Kepler-442b, and Kepler-22b. However, each of these planets has a significant flaw that can make them inhospitable. Gliese 667 Cc is tidally locked, with one side permanently facing its star; Kepler-442b has high surface temperature variance; and Kepler-22b’s star emits strong solar winds.
With so many factors influencing the emergence and continued survival of organisms, it is a wonder how life even managed to begin with all the cards stacked against it.
Image Credit by Porapak Apichodilok