Terrestrial planet Terrestrial planet A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars. The terms "terrestrial planet" and "telluric planet" are derived from Latin words for Earth ("Terra" and "Tellus"), as these planets are, in terms of structure, "Earth-like". Terrestrial planets have a solid planetary surface, making them substantially different from the larger giant planets, which are composed mostly of some combination of hydrogen, helium, and water existing in various
The Pirate Planet The Pirate Planet The Pirate Planet is the second serial of the 16th season in the British science fiction television series "Doctor Who", which was first broadcast in four weekly parts on BBC1 from 30 September to 21 October 1978. It forms the second serial of the "Key to Time" story arc. It was written by Douglas Adams, and featured some of his humour. In the serial, the tyrant Queen Xanxia (Rosalind Lloyd) and the Captain (Bruce Purchase) use the hollow planet Zanak as a spaceship that surrounds smaller planets, including Calufrax, the second segment of the powerful Key to