In my setting, there is a type of airborne fungal spore that can infect all living matter, and a Star Wars Galactic Empire style/sized faction that wants to sterilize planets with this spore inhabiting it and minimizing chances of evacuation or breaching quarantine. How should they ignite the atmosphere, or what other method that's semi-plausible and has a nice theatrical countdown to it for gameplay scenarios? Something incendiary coded is the most fitting.

Example: A fleet of ships pumping methane into the atmosphere until it can ignite the atmosphere and burn the planet. References: The Covenant glassing planets. The Empire's Death Star. I could just lift those, but somethin a lil less popular would be neat.

I love somethin dramatic, visual, and mindful of but not realism-locked by energy usage.

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    $\begingroup$ Welcome to this site. This is a good first question though you should clarify what you want more clearly. Do you want a spore that kills everything or are you generally asking for weapons to destroy a planet. If it is the later just dropping a giant space rock on them is going to work just fine. Ohh and it's visually stunning to boot. $\endgroup$ Apr 11 at 21:44
  • $\begingroup$ if you want to notify me just add @ before my name this will send a notification to me also works with other people just wanted to let you know that. Though i am following this question regardless so i will see if anything changes. $\endgroup$ Apr 11 at 21:47
  • $\begingroup$ The [magic] tag means that answers do not need to conform to any kind of scientific rigor. I could suggest that a single molecule of "burnallium" dropped into the atmosphere will magically convert the entire atmosphere into gunpowder over 24 hours so that a single spark will detonate everything. (Though an obvious frame challenge is to use magic to convert all of the fungal spore into gold.) Suggest that you may want to replace the tag with [science-fiction] at least, since you will not get a plausible answer using anything smaller than the Death Star if you change it to [science-based]. $\endgroup$ Apr 11 at 23:13

3 Answers 3


There's a method that might suit you in Alistair Reynolds' novel Redemption Ark. It is used by a machine civilisation, the Inhibitors, who seek to prevent life spreading between star systems.

It consists of vast structures around a star which generate magnetic fields that peel back the star's outer layers and let the star's fusion core expand in the direction of the planet to be sterilised. This utterly destroys the ecosystem and reduces the planet to a cinder.

The matter for these structures is obtained by dismantling a gas giant, using machinery built by dismantling asteroids. This is not a quick or stealthy method of sterilising a planet, but the Inhibitors wanted to make sure, since two separate civilisations on the planet in question had come to their attention, several thousand years apart.

  • $\begingroup$ Assuming Star Wars-esque propulsion technology, a fleet of ships with said magnetosphere-altering structures built in could likely perform this operation as soon as they reached the appropriate positions around the star, so it could actually be fairly fast provided that they were prebuilt and moved themselves to whichever planetary systems need sterilizing that day. $\endgroup$
    Apr 11 at 23:47
  • $\begingroup$ @KEY_ABRADE: You'd need a stupendously large fleet of ships to make that vaguely plausible. Stars are big. $\endgroup$ Apr 12 at 8:20
  • $\begingroup$ I had a fun night with my friend calculating how much hydrogen would be necessary to ignite earth's atmosphere and how much of that could be pulled from Jupiter or a similar gas giant. This website feels like its just full of friends like that xD $\endgroup$ Apr 12 at 17:54

One Good Plague Deserves Another

Killing all life on a planet shy of blowing the whole thing out of existence is a LOT harder than it sounds. To much life exists deep under the ground/water for even a planet wide thermonuclear bombardment to do the trick, and even if you did have enough nukes to boil away the oceans and deep glass the landscape, the aftermath of such an attack would leave much of the planet's resources ruined and the world itself uninhabitable for hundreds of generations.

Instead of thinking big, think small. The best global counter to a microorganism would be another microorganism designed to kill it off. A second plague that can only kill the fungus would eventually just learn to live in equilibrium with the fungus... unless it was designed to specifically eat itself into extinction. As it spreads, it would (like the fungus) consume all living things, but it would do it so completely that it will quickly kill off all primary producers. Once there is no more photosynthetic or chemosynthetic organisms left anywhere on the planet. Both the fungus and the counter-plague will quickly starve into extinction.

Plot Twist: Your plague you are trying to kill off could just be a weaker strain of the genetically engineered sterilization plague that has accidentally mutated to be able to leave just enough life going that it does not fully kill itself off.

  • $\begingroup$ I love the title to this, such a great mindset and feels very appropriate and a great twist to be discovered as research this faction is investigating. $\endgroup$ Apr 12 at 17:54

Not energy-restricted but also visually appealing and entertaining? Simple: irradiate every square centimeter of the planet’s surface.

Let’s examine what you’re trying to do:

  1. Sterilize the entire planet; no surviving life is allowed.

  2. Ideally, leave everything else intact. Why destroy all the valuable materials and supplies on the planet?

  3. This fungus thing seems pretty dangerous; let’s assume we’re going to allow collateral damage.

So, here’s a possible solution:

  • Set giant low-orbit space stations up that are equipped with high-powered neutron emitters. The stations aim the emitters at the ground and tune the neutron radiation temperature to damage biological life the most. Also convenient because you can then address different biologies, i.e. carbon vs silicon vs arsenic etc.; no matter what this fungus is made of, you can kill it.
  • As the stations orbit around the planet once every few hours or so, the surface is gradually saturated with radiation. If the emitters are powerful enough, one “pass” could irradiate a human with several hundred sieverts of radiation (assuming we have an adequate neutron source; maybe an onboard dirty-fusion reactor), which is lethal within a day.
  • Have various stations going around in equatorial, inclined, and polar orbits so that every area on the planet is irradiated. A constellation of 20ish stations with a 5-degree beam should be able to wipe out the planet after a few orbits.
  • Victims have a chance to escape as they see the station come over the horizon; it’s not until it’s directly overhead that you receive a lethal dose of radiation, but after that point it’s pretty much over.
  • Visually, this would be more of a horror-esque solution: strange shooting stars pass overhead, and then everyone and everything begins spontaneously rotting away before even vomiting their stomach lining out and dying. Leaves and flowers quickly wilt, birds fall from the sky, and after a few passes, vegetation is reduced to radioactive dust and people are turned into corpses, their skin having sloughed off and their DNA having unraveled like spaghetti. The fungus dies too!


  • The planet will probably be habitable again at some point in the future (or, if you don’t want it to be, it doesn’t have to; turn up the beams and neutron-activate the surface so it stays radioactive for millennia).
  • You can dive in with rad-hardened probes and snatch up all the weapons and ships and supplies and raw materials that were once guarded by the living inhabitants of the planet; the necropolises are now devoid of life and stealing from them is much easier. Besides, it’s not like their original owners will be needing them; they were probably infected with fungus anyway.
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    $\begingroup$ Irradiating the surface won’t sterilise the planet, only its surface. There is life in the deep oceans and kilometres underground that won’t be affected at all. $\endgroup$
    – Mike Scott
    Apr 12 at 16:48
  • $\begingroup$ If what’s being looked for is a way to destroy that life too, then the only real way to go is just to destroy the surface of the planet entirely (unless I’m being silly). $\endgroup$ Apr 12 at 16:49
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    $\begingroup$ This definitely has given some awesome inspiration. I LOVE the idea of a constellation APPEARING, it having a reputation in the sky and its really the orientation of a series of orbital stations designed for annihilation. $\endgroup$ Apr 12 at 17:52
  • $\begingroup$ Of course @ThunderSnug ! The only factor to consider is the fact that the stations probably would have to be deployed at a great distance; if it's powerful enough to irradiate a planet's surface from orbit, it's DEFINITELY powerful enough to irradiate the starship that's transporting it. $\endgroup$ Apr 12 at 18:42

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