Some of us, as little kids, dreamed of traveling and living on a different planet. However, as we grow up, that dream was something we believed to be impossible. After looking back to 50 or even 40 years ago, we can see how technology has advanced at light speed. By looking back, now, nothing seems impossible. Now, SpaceX has a mission to reach Mars. Could you think of humanity being an interplanetary race?
For humans to be able to survive and live on a different planet, there are some habitability factors. These factors include water, a chemical environment, and conducive physical conditions. When I say water, I mean activity of liquid water, and salinity, pH, and Eh of available water. A chemical environment means that essential elements are available. These include carbon, hydrogen, oxygen, phosphorus, sulfur, and nitrogen. Conducive physical conditions are outside physical factors. These include temperature, pressure, climate, accumulation of solar particles for UV rays, and environments.
Four kinds of habitable planets were created and are based on water. Class I includes habitats that allow liquid water to be available at the surface, along with sunlight. This would help multicellular organisms strive and survive. Class II includes habitats that initially enjoy Earth-like conditions, but don’t have the ability to sustain liquid water on their surface due to geophysical conditions. Mars, and even possibly Venus are some examples of the Class where complex life forms cannot develop. However, this doesn’t mean that water is not on the planet or that humans can’t survive on the planet. Class III are habitats where bodies of liquid water like oceans exist below the surface. However, planets in class III do not have light as they are too far from their star. Some examples include Europa and Enceladus. The last class, Class IV, are planets that have liquid water layers between two ice layers or liquids above ice. Some examples are Ganymede and Callisto.
This means that there are some planets humans can survive and live on, but there are only a select few out of hundreds.