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,
The Planets Holst taught). It was a comparatively intimate affair, attended by around 250 invited associates, but Holst regarded it as the public premiere, inscribing Boult's copy of the score, "This copy is the property of Adrian Boult who first caused the Planets to shine in public and thereby earned the gratitude of Gustav Holst." A public concert was given in London under the auspices of the Royal Philharmonic Society on 27 February 1919, conducted by Boult. Five of the seven movements were played in the order Mars, Mercury, Saturn, Uranus, and Jupiter. It was Boult's decision not to play all seven