It is not enough to have liquid water, you must have enough

We all know that so that a planet can be suitable for life It must hold water. However, this necessary condition may not be sufficient. To begin with, not just any amount of water will do. In fact, according to a recently published studythe minimum amount of this precious liquid for a planet to be a solid candidate for the search for life is much greater than we thought.

It looks habitable, but it is not.. Through a series of highly refined computer simulations, scientists at the University of Washington have shown that a planet needs to have at least 20% to 50% of the water in Earth’s oceans so that the natural cycle that sustains life can occur normally.

Geological carbon cycle. For a planet to host life it is important that it have an atmosphere, but be careful with the content of that atmosphere. Normally, volcanic activity Planetary releases large amounts of carbon dioxide into it. If this accumulates in excess, the planet becomes inhospitable to life. Luckily, there are some mechanisms that follow one another like a row of dominoes to keep carbon at appropriate levels.

In the atmosphere, some of that carbon dioxide dissolves into small water droplets and returns to the surface as rain. There, it accumulates on the rocks. Once again the rain arrives, eroding the rocks, so that carbon dioxide accumulates in the runoff waters, reaching the oceans, where it is buried at the bottom. Then, plate tectonic movements can cause carbon dioxide to rise again to the surface with the formation of mountains. It is a process that takes millions of years to occur.

Without water, everything goes to waste.. We have seen that water is an important piece of this succession. Therefore, if there is not enough on the planet, the relocation of carbon dioxide may not be enough compared to the gas that accumulates due to volcanic activity. Too much carbon dioxide in the atmosphere means higher temperaturesbecause of the greenhouse effect. As a result, what little water there is evaporates and the situation gets worse and worse.

Redefining the goldilocks zone. In astronomy, it is known as the habitable zone, or goldilocksthe region around a star that is neither too close nor too far from it. It is the ideal distance for water to remain in a liquid state. The problem is that we now see that habitability does not depend only on liquid water. There also needs to be enough water.

More refined models. In reality, models had already been created to analyze the geological cycle of carbon on planets capable of harboring life. However, the driest planets had never been taken into account, nor had as many parameters been introduced as in these more recent models, which include more forgotten parameters, such as wind. With all this in mind, we see that it is not enough for a planet to be rocky, similar to Earth and located at the exact point of its star to have liquid water. It must have enough water. If not, everything else doesn’t matter.

Image | M. Mizera / PTA / IAU100

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