The Tenth Planet of malevolent cyborgs that became a recurring adversary in later "Doctor Who" stories. The "tenth planet" in the title makes reference to a fictional lost planet in Earth's Solar System; at the time of production, the Solar System was generally held to consist of nine planets, prior to the redesignation of Pluto as a minor planet. "The Tenth Planet" is an incomplete "Doctor Who" serial – one of many serials that were affected by the BBC's policy of wiping archived programmes in the 1960s and 70s. Only three of the four episodes are currently held in the BBC archives; the
Lada Terra remnants. The most prominent region is the midlands, where gently sloping topography is disrupted by faults, fractures, and corona, making this area the most complex and studied region in Lada Terra. The western portion of Lada Terra contains a large dome-shaped structure about across termed, "the Lada Rise," which is the main highland of the region. It reaches an elevation of about and is dominated by one of the most massive corona in the solar system, the Quetzalpetlatl Corona, as well as two massive rift zones surround and partially intersect the rise. The high rises of Venus generally fall into