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. $\endgroup$ Commented 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. $\endgroup$ Commented Apr 11 at 21:47
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    $\begingroup$ 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]. $\endgroup$ Commented Apr 11 at 23:13
  • $\begingroup$ Ever read the book "This Mortal Coil' by Emily Suvada? It's YA fiction, but the worldbuilding is priceless. I'd recommend checking out the premise at the latest. might help out. $\endgroup$
    – alkahest
    Commented May 26 at 17:10
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    $\begingroup$ Not sure if we should rejoice or mourn at the number of answers. Looks like Homo Sapiens has a kink for innovative approaches to zapping planet life. $\endgroup$ Commented May 27 at 14:59

8 Answers 8


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. $\endgroup$
    Commented 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. $\endgroup$ Commented Apr 12 at 8:20
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    $\begingroup$ 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 $\endgroup$ Commented Apr 12 at 17:54
  • $\begingroup$ A solar flare inducer sounds plausible enough for the setting, just handwave that it subtly amplifies natural instabilites in the star so that the energy of one solar cycle gets released in a single giant flare, and relatively speaking doesn't need that much energy itself. $\endgroup$
    – LazyLizard
    Commented May 27 at 10:16
  • $\begingroup$ @ThunderSnug Is that you, asylum cell 35? They gave you internet access too? $\endgroup$
    – Pica
    Commented May 29 at 8:29

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. Too 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. $\endgroup$ Commented Apr 12 at 17:54
  • $\begingroup$ Life is notoriously hard to kill with a plague, and then there is a problem of killing that plague. I'd say there's zero chance it works in 24h. $\endgroup$
    – alamar
    Commented May 26 at 17:04
  • $\begingroup$ @alamar You're applying 2024 thinking to a far-future setting. One of the aspects of the movie The Fifth Element I find so charming is that from the moment Bruce Willis is introduced everything happens in 24-48 hours. I'm not a fan of "realistic" (whatever that may be in terms of a far future) so I upvoted Nos' answer and embrace the fun of a genetically-targeted artificial plague, dispensed by thousands of gas-carrying drones, that eventually burns itself out - but that doesn't matter because, due to the genetic targeting, it's not a threat to anything else. $\endgroup$
    – JBH
    Commented May 26 at 17:50
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    $\begingroup$ ... Of course, it could be a Star Wars-esque evil empire in which case some nefarious scientist might try to ingratiate him/herself with the upper crust by tweaking the genetically-targeted plague just a bit to wipe out everyone with a down-turned nose. What's a little bit of collateral damage when you're trying to save an entire planet, right? $\endgroup$
    – JBH
    Commented May 26 at 17:52

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
    Commented 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). $\endgroup$ Commented 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. $\endgroup$ Commented 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. $\endgroup$ Commented Apr 12 at 18:42

Giant space mirrors.

Napkin math says that the oceans would boil away if we 4x the energy input, it wouldn't take a lot of resources to make space mirror and they would likely already be in use for terraforming projects.

A big mirror and the the illuminated spot becomes lead meltingly hot, killing all life and likely causing long term climate issues.


Blasting them with electrons

Considering the fact that you have a Star Wars-style civilisation, doing this is a cakewalk.

Simply hook up a few Dyson Sphere to your ELECTRONLASER 4000 (Basically just a particle accelerator on steroids), and then use it to pump a b***load of electrons.

Electrons tend to repel each other, but yeah, you'll gonna eject them so fast (at ultrarelativistic speeds), they will diverge after a long time, due to time dilation effects. From the electrons perspective, they diverge apart in a few milliseconds, but from your POV, it will take millions of years to diverge.

In fact, there is a Kurzgesagt video exploring this scenario. And considering the technological advancement of the civilisation, an electron beam o' doom is basically just another Death Star laser on steroids.

We already have companies that use electron irradiators commercially, to sterilize food. So yeah, I can't see why this won't kill off those pesky little mushroo- ahem, fungi.

And bonus point, you don't need any rare element like uranium or plutonium for making electrons. Why, you can simply get them by ionizing hydrogen gas and stripping it of electrons, and then shooting said electrons at the target, killing off the nasty spores and fungi.

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    $\begingroup$ Why waste hydrogen ions? Beam them as well, for good measure. Plus, collect bonus points for not discriminating against electric charge. $\endgroup$ Commented May 27 at 14:54


Destroy the planet outright.

Use the power of a gas giant harnessed through an electronic lens, focusing on the surface, to blast a molten channel through the surface and incinerate everything.

Throw enough matter and bombs into the atmosphere to black out the sky and leave the surface glassed.

Use a superpowered laser to melt a channel into the core and out the other side, flooding the surface with the material of the core.

Ignite the atmosphere itself.

Send ordnance into the planetary crust that burrows deep and blows up a continent.

Summon undead space robots to destroy all life on a molecular level.

Or feed it to the Tyranids or Galactus.

And if everything else fails: Drop a containment unit of Gray Goo that radically and quickly eats the surface and everything. We are hellbent on destroying the planet, so why not with a nanomachine weapon that fits in the pocket of an inquisitor and leaves behind a shiny marble of a planet after it is done? The beauty of Gray Goo: a single molecule takes something on the order of 36 hours to eat the planet.

Imagine such a replicator floating in a bottle of chemicals, making copies of itself...the first replicator assembles a copy in one thousand seconds, the two replicators then build two more in the next thousand seconds, the four build another four, and the eight build another eight. At the end of ten hours, there are not thirty-six new replicators, but over 68 billion. In less than a day, they would weigh a ton; in less than two days, they would outweigh the Earth; in another four hours, they would exceed the mass of the Sun and all the planets combined — if the bottle of chemicals hadn't run dry long before. - Engines of Creation (1986)


Destroy the ozone layer or local equivalent thereof. Or the other way around: boost ozone production in the lower atmospheric layers.

On Earth, stratospheric ozone acts like superefficient sun cream: it avoids our being baked by incoming UV radiation, which is an oxidizer and large-spectrum germicide. The layer is destroyed by injecting BFC (the fire suppressant "halon") at the right altitude.
Over time, ozone regenerates spontaneously from oxygen+radiation from the nearby star.

At ground level, ozone is toxic by being an oxidizer itself. It is synthetized from molecular oxygen in lightning flashes, which fits the "grand spectacle" line of the bill.
Over a certain concentration threshold in air, it decomposes back to oxygen with deflagration: this turns the electrosynthesis of ozone to essentially a planet-size electric chair.
Else, ozone decomposes spontaneously to oxygene over time and combines ardently, even enthusiastically, with carbon. Either way, great balls of fire guaranteed.

Both approaches share the same weakness: for fastest results, local life and infecting germs must rely on oxygen-based metabolism.

  • $\begingroup$ Blasting away the ozone layer is a nice, simple, self repairing option. And while it won't kill everything the first day (as not everything will be in direct sunlight), I believe things will ramp up very quickly with how hot/cold things get and how irradiation kills almost everything. That said, this won't get the deep-sea life until all oceans evaporate. $\endgroup$
    – vinzzz001
    Commented May 29 at 9:18
  • $\begingroup$ Well, it will kill everything in 24hrs as specified IF the planet rotates in 24hrs (which is usually how the hour is defined, after all) and IF 100x their usual level of UV radiation is lethal to everyone alive in ~1hr. The OP's fungi are airborne, so it's not clear if they can infect deep-sea life. $\endgroup$ Commented May 29 at 14:08
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    $\begingroup$ In fact, the question suggests the OP's problem was only to destroy the airborne germs, and their own approach was to set the atmosphere ablaze to cook said germs. I merely suggest to cook them in UV rather than in IR. $\endgroup$ Commented May 29 at 14:18

Coronal Mass Ejection - On Steroids

I propose to you, have some device that triggers the primary star for the solar system to send out 10% of it's mass in a single ginormous solar flare. IE a spectacular Coronal Mass Ejection. Place the device in the correct location just outside the orbit of the sterilisation target, and switch it on.

It will take MUCH less than 24 hrs, but it will definately boil all the oceans, lakes, rivers and eat away the entire surface probably down to 1 or 2 kms. For a bonus slowburn, you could have it pulse, and for a plot twist, you could have the pulse create a signal that decoded gives a message along the lines of: "This planet became hostile to all life. It's sacrifice was neccesary for the greater good of all living sophonts. We Will Remember Them"

This would have SPECTACULAR visuals available. For even greater visuals and impact, you could have a similar device suck 10% or even 20% of the mass of any or all of the gas giants in the system, creating intersecting beams of total destruction, there would be some method you use to ignite the beam from the gas giants. These beams could also signal in some fasion, either a different message, or the same one.


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