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,
Planet Stories is the folk-tale, the hero-tale of our particular niche in history". Also arguing in support of "Planet Stories", science fiction critic John Clute has commented that "the content was far more sophisticated than the covers". Bradbury's work for "Planet Stories" included two of the stories that he later incorporated into "The Martian Chronicles", including "The Million Year Picnic"; only one other story in the series had appeared before this. He also collaborated on a story with Brackett, "Lorelei of the Red Mist", based on an idea of hers, which appeared in the Summer of 1946. His stories for "Planet" demonstrate