Earth's tectonic activities may be crucial to life and rare in our Galaxy

Although we can not feel it, the ground beneath us is constantly rumbling. The crust of the Earth is formed by many plate tectonics. Those plates, instead of sitting still, are constantly moving. When two plates contact, the denser plate will slip under the less dense one and sink into the Earth's mantle. Tectonic activities happen very frequently, but most of these activities are too "quiet", so we can not observe them without advanced equipment. However, dramatic tectonic activities do happen sometimes. When a huge amount of energy is released during the tectonic activity, tectonic plates shake and even deform. This phenomenon is known as "earth quake".

We always link "earth quake" to "destruction". When a severe earth quake happens, lands are ruined, buildings are fallen, and lives are taken. However, tectonic activities actually bring the "creation" of lives. According to the scientific research, tectonic activities are one of the important components to the stabilization of a planet's climate. To retain the heat from the sun, there must be some green house in a planet's atmosphere. Studies have shown that in the early stage of the Earth, green house gas was emitted from volcano eruptions. Volcanos, important valves for green house gas, are formed by tectonic activities.

Although scientists can not be sure if tectonic activities are required for lives, most of them agree that those activities are crucial to the presence of life on a planet. After understanding the relationship between tectonic activities and the climate of a planet. The presence of tectonic activities becomes a factor that scientists consider when searching lives beyond Earth. After studying many planets outside of our solar system, scientists found that the tectonic activities that we observed on Earth are actually very rare in our galaxy. Scientists found that to be able to have tectonic activities, there must be some liquid in the mantle of a planet so that the crust of that planet can flow and move. The key factor of holding liquid mantle inside a planet is the high inner temperature. If the inner temperature of a planet is very high, the metal and rock inside that mantle of that planet would be melted and remain liquid. When planets are formed, they are very hot. However, they cool down as the time past. Smaller planets lose their heat faster while larger planets hold the heat longer. Scientists believe that one of the reasons why lives can evolve on Earth is that Earth's size allows it to hold its inner heat long enough.

If tectonic plate activities are essential for lives, the chance that we find lives beyond Earth in our galaxy may be low because it is not easy to find a planet that can hold tectonic plates for a time that is long enough for lives. Scientists believe that there are about 13 billion planets that may have the conditions to sustain tectonic activities for a long time. Although 13 billion sounds much, considering how many planets there are in the galaxy, it is just a very small portion. Nevertheless, no one knows if tectonic activities are required for lives. So there are still many potentials of finding lives outside of Earth. Maybe there will be new discoveries that surprise us in the future.