TO: [mailing-list:all-employees]
CC: [mailing-list:quality-assurance], [mailing-list:facilities]
BCC: [mailing-list:galactic-villains]
Subject: Thought Experiment - removing all life from a planet

My Distinguished Employees;

I would like to take a moment to propose a thought experiment concerning our recent planetary project. The Viral Planet program was shuttered due to budget constraints, unfortunately, but it did produce excellent work from its team, as well as a number of off-shoot programs and opened the door to new challenges and opportunities.

I'd like to bring one of these challenges to the forefront. Would it be possible to devise a methodology, whether by artificial design or natural happenstance, that all life on a given planet could be removed without leaving remains such as corpses?

I understand that this has been done before by a friend of mine, but the effects were successfully undone by an independent organization dedicated to preserving the status quo. While I of course abhor the wanton destruction of all life throughout the universe, I can't help but wonder if there's a way to scale down that same effort to just a single target planet.

One could argue that acquiring the tools of the trade previously used to great effect would work in this regard, I would also remind that doing so would likely draw the attention of, and intervention by, the same organization mentioned above. So please constrain the methods of this thought experiment to non-supernatural and non-reality-altering avenues of pursuit.

To reiterate: I'm looking for a method to remove all life from a planet that does not impact the geographical or structural environment. In other words, the method may damage the atmosphere and boil the oceans, but must leave buildings, cities, and geographical landmarks unscathed.

Thanks for Your Attention,

B. B. Calamity
Chief Executive Officer
Intergalactic Engineering and Design


To: [mailing-list:all-employees]

From: Carl Llama

Date: June 5, 2019

Subject: Re: Rumors

In response to the rumors circulating the office after Mr. Calamity's email, I reached out to the CEO. He assures me that there is no intention of the results of this exercise to be available to outside organizations, that the methodology resulting from this exercise will never be used on Earth, and that no employee will be held accountable for any disaster that befell a world that suffered a fate reminiscent of this thought experiment.

This question is not a duplicate of this question because that one has as its criteria "before the end of 2025 to destroy all life on Earth within a 30-day period." This question specifies neither a constraining date (2025) or a timeframe of action (30 days).

Further, these two questions differ in regard to a specific constraint defined here and not in the other question:

without leaving remains such as corpses

Here is a link to a relevant Meta post about judging when answers may be duplicates of each other.

  • 1
    $\begingroup$ Please note that a Very Large Number of endolithic / lithophile microörganisms live in the rocks themselves, down to at least three kilometers. (Three kilometers is the limit to which we have dug and looked for them, not the limit of their endurance.) As a consequence one cannot really annihilate "all" life and not destroy a large part of the crust in the process. $\endgroup$
    – AlexP
    Commented Jun 5, 2019 at 14:48
  • $\begingroup$ In Allistar Reynolds Redemption Ark all life on the planet Resurgam is eliminated by the Inhibitor Maschines, but they turn the star into a particle beam weapon to do it and even then they cook the planet for weeks until it has lost a significant portion of its mass. Few things short of such violence will kill everything, including the organisms mentioned by AlexP. $\endgroup$ Commented Jun 5, 2019 at 15:00
  • $\begingroup$ side note: the formatting you have chosen gives a ... preview in the main page. It made me think of a non typed question. $\endgroup$
    – L.Dutch
    Commented Jun 5, 2019 at 15:30
  • $\begingroup$ @Halhex This is not a duplicate; see my edit. $\endgroup$
    – Frostfyre
    Commented Jun 5, 2019 at 16:20
  • 1
    $\begingroup$ Relevant meta question, for close/reopen voters to check out: worldbuilding.meta.stackexchange.com/q/7364/627. $\endgroup$
    – HDE 226868
    Commented Jun 5, 2019 at 18:06

5 Answers 5


To: "Carl Llama"

From: "The New Guy"

Date: June 5, 2019

Subject: Watch Out

Dear Mr. Llama,

Watch your back. This looks like a setup. I'm new here, but what you're asking can't be done. Life is just too robust, and cities are too fragile.

You can't burn out the bacteria miles underground because those cities can't stand too much heat. The concrete will de-hydrolize and the buildings will collapse.

You can't expose the world to intense enough radiation because the molecular structure of those precious cities will change, and the buildings will collapse.

You can't do much underground without making the crust shift, and even small crustal changes will shake the surface, and the buildings will collapse.

If you try to do something slowly, life will evolve to adapt to your change.

If you put your reputation behind this project, the only thing killed will be your future with Universal Cleaning Company. Watch your back. You may be in Calamity's sights.


Let's grab the classics:

Colony Drop!

We all know the premise of Gundam, don't we? Humankind went to the stars, then Earth wanted to oppress the colonies. The Colonies flipped the terran eagle and put thrusters on any and all space stations and craft they had and put them on full thrust - course: earth. They ensured widespread destruction of society... but not total annihilation because they had too little mass. So instead of scattering colonies all over the planet, we go a step larger and drop the largest and closest place that could be colonizable onto earth: The moon.

To get it to deorbit in chunks large enough to annihilate all life as we know it and send the planet into an ice age, we just need to crack it into good-sized chunks. A good plan would be to dig deep from the far side of the moon and then detonate a couple dozen nuclear warheads, separating the moon into maybe three or four chunks that start to descend onto earth. The good part: Humanity has no chance to survive. The bad part: Life itself has a chance to. So, we need to go bigger.


We want to exterminate the whole planet? Then we should go all in. Calling upon the Imperium of Man's wisdom: We drop a torpedo onto the planet that incinerates the whole atmosphere and leaves all life to suffocate. Or we drop a bomb that bores to the core, then destabilizes it by blowing it up, making the whole planet to erupt in volcanos and turn its crust inside out.

Vogon Construction Crew

Why make our own fingers dirty? Call upon the Vogon construction crew to place a hyperspace lane right through Sol III. They'll finish it up easily. Just make sure they don't forget to place a checkmark on the papers.


We could also drop bioengineered creatures onto the planet that eat all of the lifeforms on it and leave a dead husk, possibly containing the new spore cell for the next species' demise, should they stumble over their eggs...

Poison the Sun

But we have unlimited time and resources, right? So let's start to ship all the iron and other metals we can find right into the sun. As we start to drop more and more material into Sol, we start to heat it up - and make it consume its hydrogen faster and burn hotter. At some point - once we have dropped several percents of the solar mass into it (earth is less than 0.000303%!), Sol will start to cook Earth, shifting the habitable zone outwards and past Earth. Solar winds will ravage the planet and possibly rip away its atmosphere while the increased output of the sun will turn the blue planet into a white clouded ball with boiling oceans and an average temperature of more than 50 °C - enough to denature any protein and make life as we know it impossible.

Wait around 5 Billion Years.

But why cook earth? We have no time constraints. We can have time itself turn Earth inhabitable for all life by just letting the sun consume all the Hydrogen and turn it up to carbon. Sol is not massive enough to support the fusion to anything larger than carbon and then will start to shut down. The result is, that earth will soon after - in astronomical terms - freeze into a ball of ice, showing only remnants of life, encased in ice. At that point, any remains of human society have been eroded away.


The simplest answer already exists, has been built, and tested back in the 1950-1960s.

The Neutron bomb is a low yield thermonuclear weapon specifically tweaked to enhance the production and release of neutrons.

While the immediate blast radius is much smaller than most nukes, it still damages that radius, so care in deployment is required. However the neutron shockwave is more widespread, and lethal to organic lifeforms.

Current technologies can produce this weapon, and with careful application, only carefully fortified strongholds and the heaviest of armored vehicles offer any degree of protection against the neutron shockwave.

With certain theoretical advancements in technology, steady neutron production could be enhanced and stabilized. Neutron blocking material already exists, once neutron reflective material is secured, then directed neutron energy weapons become possible.

Such a naser weapon [Neutron Amplification (by) Stimulation (of) Emitted Radiation] could be used to sterilize organics with minimal impact on most inorganic materials.

Atmospheric dispersion is still an issue, causing the neutrons to lose energy and eventually be absorbed, so range is limited.


If the neuron option proves undesirable, then a tailored genetic virus which is tweaked in an effort to limit what species it affects, and also completely breaks down the structure, might be possible.

Mutation always remains a risk, however.

  • $\begingroup$ Expect neutron bombs aren't as effective as they're supposed to be when it comes to leaving structures intact, neutron activation in city materials causes radioactivity and results in weird and destructive secondary chemical reactions involving decay products. $\endgroup$
    – Ash
    Commented Jun 5, 2019 at 18:47

To: Who It May Concern

From: Dr. Vahlen's Eager Lab Assistant

Dr. Vahlen hasn't yet had the time to think through this proposition, and, to be frank, the Commander and Bradford have both agreed that she does not need to, because it would only give her ideas. So they assigned the job to me.



All forms of life can be lethally killed with enough radiation. The key phrase here is, of course, enough. 400 to 450 rem over a short period can kill off half the human population within thirty days. That's about 4 sieverts, or 4 joules/kilograms. (Radiation uses weird measuring units.) That's the far end of the spectrum. The other end are radioresistant bacteria which can survive up to 30,000 grays, which is apparently the same thing as a sievert. (I'm just going to use grays from now on. Remember, 1 gray = 1 joule). The good new is that once you decide to bombard Earth with the amount of grays necessary to kill even the most resistant of bacteria, you don't really have to worry about anything else surviving. The bad news is, ah, getting that much energy. The Earth's crust is only a about twenty or so miles deep. That only gives you about 1.5*10^10 cubic miles to irradiate to the point where even a bacteria, which is fills up a space of about 1.4*10^-14 cubic miles receives that much radiation. Good luck!

  • $\begingroup$ And that much ionising radiation will cause secondary radioactivity in structural materials and the collapse of every concrete building on Earth. $\endgroup$
    – Ash
    Commented Jun 5, 2019 at 18:50

I believe nanobot swarms, mixed with chemically altering the oceans and atmosphere might be an answer. Theoretically you could program the bots to build themselves, and use advanced AI to encourage them to follow their prime directive. The biggest issue is the small bacteria that live deep underground, and do not rely on oxygen to survive. For total annihilation I think a good goal of the swarm would be to destroy the atmosphere of earth so it looks like Mars, or increase the atmosphere's density until the planet resembles Venus.


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