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,
Gustav Holst found his genuine voice in his setting of Whitman's verses, "The Mystic Trumpeter" (1904), in which the trumpet calls that characterise Mars in "The Planets" are briefly anticipated. In this work, Holst first employs the technique of bitonality—the use of two keys simultaneously. At the beginning of the 20th century, according to Matthews, it appeared that Holst might follow Schoenberg into late Romanticism. Instead, as Holst recognised afterwards, his encounter with Purcell's "Dido and Aeneas" prompted his searching for a "musical idiom of the English language"; the folksong revival became a further catalyst for Holst to seek inspiration from other