The planet Dolumar V is subjected to Exterminatus after a battle between the Imperium, the Tau, and the forces of Chaos. Cyclonic Torpedoes are launched at the site of a Chaos Temple, in order to wipe out anything tainted by Chaos.
Afterwards, the temple site is directly bombarded by the Imperial fleet, with enough firepower to crack the planet's crust.
Exterminatus or Exterminatus in Extremis, is an order to destroy a planetary biosphere in the Warhammer 40,000 universe. Typically used only as a last resort, when the price of holding or retaking the world is deemed to be too high, or the threat of mutation or heresy too great to contain by conventional means. Typically, the order may only be given by a high-ranking Imperial Warmaster, or a member of the Inquisition.
Exterminatus can be carried out in many different ways. The most common is an orbital bombardment, which can be done through the conventional firepower of the Imperial Navy. Typically, however, special weapons are used, designed to destroy all life on a planet's surface.
Virus Bombs release a special type of virus designed to quickly spread and destroy all organic cellular structures, reducing all life on the planet's surface to a mass of slime. This process also releases millions of tons of flammable gases into the planet's atmosphere, and as a final touch, the Virus Bombs ignite this gas, turning the atmosphere into a firestorm that usually takes out anything the virus somehow missed. Only those who may have escaped into specially-made shelters deep underground can survive a Virus Bomb attack. The population of the planet Tallarn managed to escape complete destruction this way, but the once-verdant world was forever transformed into a desert.
Cyclonic Torpedoes are more direct in action, immediately igniting the planet's atmosphere.
During the 13th Black Crusade, Lord Castellan Ursarkar E. Creed ordered a massive reactor on the prison world of St. Josamine's Hope to be overloaded when it seemed that the forces of Chaos would finally take the world. Rather than a nuclear meltdown, the reactor exploded, blowing the entire planet apart.
There are also, rarer, more specialised weapons capable of inflicting exterminatus upon worlds with no atmosphere or biological material (so called Necron Tomb Worlds are the main example). These typically take the form of special torpedoes, equiped with a two stage warhead. The first warhead is a melta charge, which cuts a hole throught the planetary crust, allowing the rest of the torpedo to penetrate the core of the planet. The second stage of the warhead is a modified cyclonic warhead, which upon detonation destabalises the planetary core. This is sufficient to physicaly destroy the planet in most cases.
References
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See also
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