Vulcan (Invasion of the Daleks)

Vulcan was a planet in Earth's solar system (COMIC: Invasion of the Daleks) which supported a human colony. (TV: The Power of the Daleks)

Overview
Vulcan was a young volcanic world with fertile soil and no native life. (PROSE: The Power of the Daleks) The length of its day was only about an hour shorter than Earth's, and its atmosphere was breathable by humans, with an oxygen density of 172, no radiation, and a temperature of 86 degrees Fahrenheit (30 degrees Celsius). Among the volcanic sand and ash were pools of fuming mercury. (TV: The Power of the Daleks) Vulcan's day was several hours shorter than Earth's. (PROSE: The Power of the Daleks)

According to one account, Vulcan was the closest planet to Sol in Earth's solar system. (COMIC: Invasion of the Daleks) By another account, Mercury was the first planet, (AUDIO: The Satanic Mill) making Earth "Sol III", (TV: Voyage of the Damned) and Vulcan was either many parsecs from Earth, out on the frontier, (PROSE: The Power of the Daleks) or in the Museum of Things That Don't Exist. (PROSE: The Taking of Planet 5)

History
Vulcan was first discovered in 1859. (AUDIO: The Pursuit of History)

Vulcan was colonised years before the Dalek invasion of Earth in the mid-22nd century. (PROSE: The Power of the Daleks) By 2136, Terri Willis told Ben Jackson that Vulcan was "practically a legend". (PROSE: The Murder Game)

After humans discovered the mineral riches of the planet, it became humanity's third ever colony, as Earth was suffering from mineral shortages at the time. It was owned and funded by the Interplanetary Mining Corporation, who sought to keep things "economical" by providing the colony with the bare necessities of technology and equipment, stifling efficiency and increasing danger on the planet and in its mines. This built up resentment, and a band of rebels began plotting against Governor Hensell, whom they viewed as an IMC mouthpiece. At the time, the nearest human settlement was twelve parsecs away. (PROSE: The Power of the Daleks)

Early in the colony's history, a crashed spacecraft was discovered underground. At the same time as Bragen's rebellion against Hensell, it was reactivated by Lesterson, releasing Daleks who began an indiscriminate slaughter of the colonists. However, the Second Doctor arrived and overloaded their temporary static circuit from the colony's electricity supply (TV: The Power of the Daleks) with a device made by Magpie Electricals. (HOMEVID: The Power of the Daleks) The Daleks that survived this encounter with the Doctor were classified as insane and were sent to the "intensive care" section of the Dalek Asylum. These Daleks were later destroyed when the Dalek Parliament blew up the planet. (TV: Asylum of the Daleks)

Quinn became Governor in the aftermath of the rebellion and the Dalek attack. (TV: The Power of the Daleks) As he left, the Doctor knew that the terraforming would succeed and Vulcan would be covered with greenery and new cities. (PROSE: The Power of the Daleks)

The Seventh Doctor and Elizabeth Klein visited the mercury swamps of Vulcan prior to their arrival on the Vrill colony. (AUDIO: Survival of the Fittest)

When the Daleks planned to invade Earth's solar system in 2400, Vulcan was on their map between the Sun and Mercury. The Golden Emperor worried that humans would soon have colonies on every planet of their solar system. (COMIC: Invasion of the Daleks)

Vulcan appeared as an exhibit in the Museum of Things That Don't Exist. One sponsor of the museum believed Vulcan was invented by Star Trek. (PROSE: The Taking of Planet 5) Vulcan was the home planet of the Vulcan species from the Federation universe (COMIC: Assimilation²) and the fictional Star Trek series. (PROSE: The Slow Empire)

Behind the scenes

 * In the 19th and 20th centuries, Vulcan was a hypothesised planet between the Sun and the orbit of Mercury. While the theory has since been discredited, such a planet was shown in a chart of the solar system in Invasion of the Daleks, a 1964 comic story by Terry Nation and David Whitaker, and then featured prominently as the setting of Whitaker's 1966 Second Doctor television story The Power of the Daleks. However, later stories would establish that Mercury was the closest planet to the Sun, and John Peel's 1993 novelisation of The Power of the Daleks depicted Vulcan as existing many parsecs from Earth and "quite a way out on the frontier" around a "fledgling sun". The Taking of Planet 5 referenced the dispute by including Vulcan in the Museum of Things That Don't Exist.
 * The Star Trek character Spock came from the fictional planet Vulcan, which debuted on screen just two months before Vulcan appeared in The Power of the Daleks aired. Both shows seem to have selected the name independently.