Titan is the only satellite in the solar system to have an atmosphere composed primarily of nitrogen. There are lakes of liquid hydrocarbons on Titan, there seems to be a methane cycle, as on Earth there is a water cycle. Io has active volcanoes, and the surface is changing very quickly. Europa, Ganymede, Callisto are covered with a thick layer of water ice.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.