We are very much aware of how astronomers qualify Mars as a habitable location for humans. This appears to be their top priority, given all their explorations of the Red Planet.
Yet, there are still other planets in the universe that might be a viable choice and most likely exist outside the habitable zone. So, the question is, can life exist on these planets?
What Is a Habitable Planet?
According to NASA, a planet is considered habitable if it can support life for a considerable amount of time. The availability of liquid water is one of the primary requirements that must be present on the planet's surface.
The primary importance of water and how temperature impacts a planet's ability to support life.
Based on the simulations performed by astrophysicists, a planet's water content has a significant impact on how easily it can convert into an ice ball.
According to Space.com, a planet like Earth can freeze with just an 8% drop in sunlight. However, drier worlds are more resilient, extending the limits of habitability further than we can currently go and increasing the chances of discovering life elsewhere in the universe.
Planet's Behavior When Exposed to Sunlight
The astrophysicists were able to better understand the complexity of the topic by using computer simulations. It helps them investigate how various types of planets might behave and evolve in their home systems.
The planets' temperatures, reflectivity, the quantity of sunlight they receive, and the presence of water were taken into account. The reason for the consideration of reflectivity is that the energy that simply reflects off the surface and escapes into space does not contribute to warming. The amount of moisture in the air is considered because it promotes the greenhouse effect, which can warm a planet.
Research Results on the Impact of Sunlight on a Planet's Habitability
Changing the amount of sunlight that land planets receive allowed an international team of scientists to study the evolution of those planets. They discovered that a planet freezes when it is overly cool, which is not surprising.
However, they also discovered that land planets can outlive their Earth-like aqua counterparts by a significant margin, the researchers revealed in an article posted to the public archive arXiv in November.
The research suggests that some of the planet's liquid water freezes when it experiences a slight cooling. Since ice is far more reflective than water, the small amount of extra ice deflects more sunlight, which stops the sun from further warming the globe.
As a result, the planet becomes somewhat colder, more ice develops, and the reflectance increases slightly.
The reverse runaway greenhouse effect takes place when this process repeats. According to the scientists, under this scenario, the globe transforms into a massive snowball.
On the other hand, if the sun's heat increased, a planet like Earth would change into something more akin to Venus. As it heated up, it released more water into the atmosphere, which trapped more heat and released more water. A runaway greenhouse effect arises in this scenario.
Considering Land Planets as Livable Planets
Land planets will always have less water vapor in their atmospheres because they don't have much moisture.
According to the simulation, a land planet could be placed around a star that emits 80% more heat than the sun and survive quite well. It means that we may consider an Earth-sized planet beyond the standard habitable zone to be livable if we discover it.
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