Terrestrial planet from the original solar nebula. The Solar System has four terrestrial planets: Mercury, Venus, Earth, and Mars. Only one terrestrial planet, Earth, is known to have an active hydrosphere. During the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. Dwarf planets, such as Ceres, Pluto and Eris, and small Solar System bodies are similar to terrestrial planets in the fact that they do have a solid surface, but are, on average, composed of more icy materials (Ceres, Pluto and Eris have densities of 2.17,
Emanuel Swedenborg well as spirits from planets beyond the solar system. From the 'encounters', he concluded that the planets of our solar system are inhabited and that such an enormous undertaking as the universe could not have been created for just one race on a planet or one 'Heaven' derived from its properties per planet. Many Heavenly societies were also needed to increase the perfection of the angelic Heavens and Heaven to fill in deficiencies and gaps in other societies. He argued: "What would this be to God, Who is infinite, and to whom a thousand or tens of thousands of planets,