Artistic vision of the planetary system
Researchers at the University of Pennsylvania believe that there may be living worlds without plate tectonics. When searching for habitable worlds, scientists are looking for the biosignals of atmospheric carbon dioxide. On Earth, it increases surface heat through the greenhouse effect. Carbon also goes into the subsoil and back into the atmosphere by natural processes.
Volcanism releases gases into the atmospheric layer, and then through weathering, carbon dioxide is drawn out and absorbed by surface rocks and sediments. Balancing the two processes keeps carbon dioxide at a certain level in the atmosphere, which is important for whether the climate is temperate and suitable for life.
Most of the terrestrial volcanoes are located on the border of tectonic plates. This was one of the reasons why it is believed to be an important criterion for the search for life. The crevice, where one plate slides deeper beneath the surface, also helps in the carbon cycle, pressing carbon into the mantle.
On planets without tectonic plates, the crust is a solid giant spherical plate floating on the mantle. Such worlds are considered more common than tectonic ones. To be precise, the Earth is the only planet with confirmed tectonic plates. Therefore, the researchers decided to create a computer model of the life cycle of the planet. They studied how much heat is able to maintain climate depending on the initial budget or the number of fuel elements present at the time of planetary formation. Some elements emit heat during the decay. Running hundreds of simulations (changing the size and chemical composition of the planet) showed that planets without plate tectonics are capable of maintaining conditions for liquid water for billions of years. In extreme cases, it is possible to hold out over 4 billion years, which is almost equal to the age of the earth.
In these worlds, there are also volcanoes, but they do not work so often. At a sufficiently high temperature and pressure, carbon dioxide leaves the rocks and makes its way to the surface (degassing). On Earth, this is done with water in the zones of subduction faults. The degassing process increases depending on the types and quantities of heating elements located on the planet. So scientists get new indicators of the life potential of the planet.
