In the early period of our solar system, other planets looked more like Earth than they do today. On Mars and Venus, for example, volcanoes were active and they had a denser atmosphere. Like Earth, Mars had liquid water on its surface and a magnetic field that protected the planet from dangerous radiation from the Sun. In several places on Mars the conditions were favourable for life. Could life have arisen on all these young planets? Or were only the conditions on Earth the right ones?
If we now look at these three planets, we can see that the Earth, Venus and Mars, however, developed completely differently over time. The earth is now the only one with a strong magnetic field and liquid water. Venus has a very dense atmosphere while Mars now has a very thin atmosphere. On Venus it is constantly hot, while on Mars the temperature between day and night varies by almost a hundred degrees Celsius. The earth has plate tectonics that ensure a continuous circulation of substances such as carbon and water. It is therefore not very probable that life would still arise on Venus or Mars.
However, there are other places in our solar system that have undergone a completely different development, such as the ice moons Enceladus and Europa. There we find oceans of water under a thick layer of ice. We expect to find sources of heat there that keep the water liquid. Do these heat sources