In the Victorian era, before the discovery of radioactivity, there was a scientific mystery - scientists could not understand why the Earth did not turn into an ice ball over billions of years of existence. No matter how hot the initial mass of stones and dust, from which the planet was formed, during such a period in cold space it should not just cool down, but be covered with a multi-kilometer crust of ice. Modern calculations confirm this - at the current position in the solar system, the Earth does not receive enough heat from the star to keep the liquid ocean on its 75th surface.
Today we know that the reason is in radioactive elements, which constantly release energy, and their excess in the Earth's core keeps it hot and liquid. Without this heating, at a certain stage of its existence, the partially cooled planet would be covered with water from pole to pole, which would then naturally freeze. However, on Earth, water evaporates, saturates the atmosphere, falls in the form of precipitation - all this made it possible to ensure the circulation of substances in nature and start the carbon cycle that gave rise to life.
But why is the Earth so alone in the solar system, do other planets not get radioactive elements? Yes, that's right - modeling by astronomer Michael Meyer from the University of Michigan showed that in prehistoric times, in addition to the Sun, there was another giant star not far from us. And when the planets were just forming, it turned into a supernova, throwing a lot of radioactive debris into space. And most of them were received by the Earth, "successfully" falling under the ejection.
Understanding these processes should make it easier to find exoplanets, Meyer said. The main criterion for the presence of life is not water, but a sufficient amount of radioactive elements in the body of the planet to maintain it in a liquid state. This is another critical filter for weeding out deliberately unpromising options.