What if the Earth that we know today is like what Venus was millions or billions of years ago? What if the Venus that we know today will become the fate of the Earth millions or billions of years later? What if the Mars that we know today will become the next Earth millions or billions of years later? What if Venus was once Earth --- was once habitable? If so, will Mars become habitable, too?
Ladies and gentlemen, let me share with you my thoughts about this that have been here in my head since I was 12 years old. Normally, I would personally talk about this to people that have the same interests as I have.
Earth as a living planet
In our elementary and high school discussions, solar system and all that it contains were tackled including the Earth and why it is habitable.
Source: NASA
So, why is Earth very special that it is the only planet in the solar system (or the only planet that we know so far) that can support life? Here are some qualities that a planet should have to support life based from American Museum of National History and Genetic Science Learning Center:
- It has a right distance from a star --- not too near to be exposed in extreme heat and not too far to get extremely cold.
- It is made of rocks.
- It is big enough to have a molten core.
- It has a protective atmosphere.
- It has the right composition that can support life (i.e., water and carbon)
Sun as a heat source
As I mentioned above, item 1, that a planet (in this case, Earth) must receive the right amount of heat needed from the star (in this case, the Sun) or a planet must have the right distance from the star to receive the right amount of heat. We all know that the Sun is a star, the only star in the solar system, at least. According to University of Southern Maine, "as the Sun ages, it slowly grows hotter due to the accumulation of residual energy emitted by these core reactions".
Source: NASA Earth Observatory
Venus as the Earth's twin planet
Source: NASA
It has been known to us that Venus is the planet that is slightly similar to Earth in terms of size, mass and composition. However, Venus has a very thick atmosphere and an extremely hot surface temperature. It does not have water in it. But according to NASA, it "may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer modeling of the planet’s ancient climate." According also to NASA:
Previous studies have shown that how fast a planet spins on its axis affects whether it has a habitable climate. A day on Venus is 117 Earth days. Until recently, it was assumed that a thick atmosphere like that of modern Venus was required for the planet to have today’s slow rotation rate. However, newer research has shown that a thin atmosphere like that of modern Earth could have produced the same result. That means an ancient Venus with an Earth-like atmosphere could have had the same rotation rate it has today.
Scientists long have theorized that Venus formed out of ingredients similar to Earth’s, but followed a different evolutionary path.
So here's my hypothesis: Many years ago, when the Sun was young and less hot, its temperature was enough for Venus to have a modern Earth-like condition. It might have supported life long before the Earth started supporting life. But as the Sun grew older and hotter, Venus became extremely hot and inhabitable. Following this logic, inevitably, the modern Earth will suffer the same fate as Venus. Thus, giving us a hint that the next habitable planet in the solar system will be Mars, which is currently covered with ice caps. So, can we call ourselves lucky to have lived in the generation where the configurations of a planet and a star are just right to support life?
What's next?
Everything I shared was just a hypothesis based on the facts I know. If you find some errors and additional input, please let me know. What are your thoughts about this?