Have you ever heard of the Goldilocks zone?
Astrobiologists are so passionately and so persistently looking for extraterrestrial life that they will eventually find it. There is no place in which they do not look and in which they do not measure the conditions.
And then they find conditions for life even where there are none.
For example, Venus is a harsh and extremely unsuitable place, but astrobiologists high in the clouds of that planet find a place where there is a comfortable temperature and say: “There could be life there.”
Then on planets that are tidally locked and eternally turned on one side towards their star and on which the temperature equal to the temperature of a blast furnace reigns, and on the other side the rock cracks against the cold they find that between those two spheres of the planet it is very pleasant.
And then, deep under the ice crust on Europa, they found that there is an ocean, very convenient for life, and so on. They would also find a convenient place to live in the hot oven in which you bake a pizza. Somewhere near the fan…
They are so persistent that they will really eventually find life.
But what have astrobiologists discovered so far?
They’ve discovered that water is the most important thing for life, because here on Earth, where there is water, there is life, almost certainly. That is why astrobiologists are looking for places where there is water in space (Mars, Enceladus, Europe…). Maybe life could do without water, we just don’t see how.
Water, as we all know, is ideal for life.
However, in order for water to play its important role in sustaining life, it needs to be liquid – which depends on the pressure to which it is exposed.
If it is surface water, then that pressure is exerted by the atmosphere. But let’s forget the atmosphere and pay attention to another factor needed for liquid water, which is temperature.
If it is too high, the water evaporates, if it is too cold, the water freezes.
Life lives between those two extremes. Venus is too close, Mars is too far from the Sun, and Earth is just right. In a childish fantasy, astronomers called the space in which the Earth orbits the Sun the Goldilocks zone, because life there reminded them of that girl with gold-colored hair who liked her porridge neither too hot nor too cold, but lukewarm, so life also likes a moderate climate.
In the beginning, in the distant past, Venus and Earth were the same in size and atmosphere. But they were at different distances from the Sun, which was crucial for the origin and evolution of life.
Because the Earth was far enough from the Sun that its water vapor condensed into clouds and fell to the ground as rain, thus creating the oceans.
Of course, it had to rain a lot, and it rained for an incredibly long time: for millions of years, continuously. Some consider even tens of millions of years.
Along the way, the carbon dioxide was washed away and dissolved in the oceans and seas. This could not have happened on Venus, because it was too warm for water vapor to condense in the atmosphere.
The volcanoes spewed carbon dioxide that remained in the atmosphere and the atmosphere grew, becoming denser and thicker, and the carbon dioxide remained in it – and prevented the planet from cooling.
Because the Sun’s rays passed through the atmosphere of Venus, they hit the ground and heated it up. But the thermal (infrared) radiation emanating from the ground cannot penetrate the carbon dioxide clouds and that radiation is trapped.
So, Venus heated up and overheated and today it has a temperature of 464 degrees Celsius – on average, and life as we know it cannot withstand that.
Mars is at the other end of the Goldilocks’s zone, ie. on the outer edge of the habitable zone. It has a temperature of -65 degrees Celsius and water on the surface of Mars cannot be in a liquid state.
And if someone were to spill liquid water on the surface of Mars – it would evaporate quickly, because the atmospheric pressure on Mars is low (the lower the pressure, the water boils and evaporates at a lower temperature), and then it would disperse into the interplanetary space.
And that’s it.
Astrobiologists are therefore looking for a planet in the Goldilocks zone in space, because there they expect liquid water, and then life.
