In my world, the humans left Earth a few centuries ago because it was too heavily polluted with chemical smog. They've settled a new planet and have so far managed to keep it clean. However, they are looking to restore the Earth and conduct periodic checks on its health and the state of the chemical pollution.

The current situation is this. The last check on Earth revealed that the chemical pollution is now negligible. So, the humans filled up a spacecraft with supplies, a team of 10, and enough fuel to get to Earth. However, these astronauts get there, land, and soon discover that they're not safe: although the chemical pollution is less potent, one of their number drops dead after a few days from chemical poisoning. The chemical smog is a mixture of a few chemicals: primarily carbon monoxide, with some vaporised phosgene and (just for variety) some LPS.

The question now is how the remaining 9 could survive until their rescue ship arrives in a years' time, given a 5-4 split of women to men and anything from the 21st century that might have survived on Earth. Assume they know their way around and have enough skilled people that they can use any method of transport; additionally, they have brought a 21st century nuclear fission reactor with them for power. Their ship can support them for 5 days each month before the oxygen runs out and needs to recharge.

What methods could they use to avoid chemical poisoning?

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    $\begingroup$ Irradiation or poisoning? There's a big difference... $\endgroup$ – Tim B Dec 29 '14 at 16:15
  • $\begingroup$ @TimB Knew there was something wrong. Edited $\endgroup$ – ArtOfCode Dec 29 '14 at 16:17
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    $\begingroup$ Treatments/prevention methods for different kinds of poisons are vastly different. Without information on what kind of poison, it would be impossible to give an answer. VTC unless the question is specified in more detail. $\endgroup$ – March Ho Dec 29 '14 at 17:09
  • $\begingroup$ @MarchHo Edited that in $\endgroup$ – ArtOfCode Dec 29 '14 at 17:11
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    $\begingroup$ Why can their ship only support them for 5 days a month without recharging? How'd they survive the trip to Earth with that limitation? $\endgroup$ – GrandmasterB Dec 29 '14 at 17:36

It seems to me there are only a few ways to approach this:

  • Develop an immunity (pro-active)
  • Develop a filter (counter-active)
  • Develop an antidote/medicine (re-active)

The problem is that we need more details (from you, the author) about what this chemical is. What it is nearly exclusively determines the "right" approach and determines how their experimentation goes.

For example, if the "chemical" is made up of primarily thick particles that're just omnipresent in the air, then water over a piece of clothing might make a good filter. Then all they need to do is (1) realize this and (2) make a filter for a hut or something and have a fan blowing, creating a positive-pressure safe cabin.

If it's a chemical which slowly enters the bloodstream, slowly causing damage until it just gets too far... then it's probably already too late for them.

But you should:

  • Think about what you want the solution's form to be (see above list)
  • Find chemicals which might plausibly be in the atmosphere that would cause this
  • Perhaps re-ask the question (or edit your current one), including more information about the technology they have on their ship (i.e. do they have a science lab? Or is it JUST a lander, like in "The 100")

Added details after the chemical composition is added:

From what I'm reading about phosgene and LPS is that their symptoms are likely to go unnoticed by the landing party for a while. The CO is more likely to be noticed from the effects more immediately (well, I guess this depends on the density).

As Serban Tanasa mentioned, it is suspicious that the advance scanner didn't detect it - especially given the CO.

I think your chemical composition (and, more generally, the focus on the chemical pollutant) may be complicating things for you. You may want to find one thing which:

  • A "standard" batch of scans might not detect --or-- may be pushed away from the lander causing it to not detect it

  • Gives at least some [noticeable] hint as to what it may be

Things to explore:

  • Stuff in the air (like chemicals) (which you've already done)

  • Stuff that's just present (like radiation)

  • Stuff that's on stuff (like a powdered chemical on food sources or the ground)

  • Stuff that's in stuff (like a mutation in a plant that used to be safe but is now poisonous)

  • Stuff that you haven't developed an immunity to (like a flu which your immune system has never been exposed to before)

  • Stuff that lives in people (i.e. parasites)

Parasites could give you an interesting angle: you could simultaneously explain why it wasn't detected by the scanner AND why it's affecting people at different rates by saying that there aren't that many of them per acre.

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  • $\begingroup$ +1 for more info about the chemical. Definitely a "depends" question $\endgroup$ – Brian Robbins Dec 29 '14 at 17:06
  • $\begingroup$ I've added detail about the chemical composition. $\endgroup$ – ArtOfCode Dec 29 '14 at 17:12

Depends on what kind of chemical we're talking about. Now, if this were a murder mystery, the fact that 22nd century tech was unable to detect it prior to landing, or even with ground-based measurements immediately after landing should be a strong clue.

What could be going on? What kind of hidden chemical would slip past the paranoiacal kind of detection filters that human survivors from a humanity who lost billions to poisoned air less than a century before would think to put in place?

I would probably relax the "chemical" part of the poisoning a little bit. After all, it's implausible that a persistent chemical would avoid spectrometry readings and air samples taken on landing.

So something must have changed after landing. That suggests a biological source. Bingo: a native plant or fungus has done a punctuated-equlibrium-style evolutionary jump in reaction to say, high levels of some (man-made) poison in the soil and is now employing it to drive away predators or kill neighbouring plants. It just happened to have enzymatic manipulators that closely matched the signature of some particular poison chemical, so a few mutations under the heavy evolutionary stress of complete ecological collapse and voila!

The arrival of the human aliens back on earth unfortunately coincided (or somehow triggered) the blooming cycle of the nearby Wolfsbane, whose deadly polen or oils or whatever is spread into the air by wind or some resistant bumblebee, and inhaled by your hapless explorer (or maybe he walked through a field, or merrily rolled down a flowery hill)


  • Catch some bees, extract some antidote.
  • Move ship out of the poisoned blooming clearing (although who knows how many other plants adapted to use the now-ubiquitous poisons in the soil?)
  • Develop some chemical neutralizer for the specific poison detected in the dead explorer. (again, other plants might bloom later with new poisons)
  • Wear masks and bodysuits. Don't roll in flowerfields :)
  • Create chem-filtering textured tents if cannot sleep in sealed spaceship
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  • $\begingroup$ That's a good point about detecting it. If it's a slow-moving or slow-building chemical, the landing itself may have pushed it away. Or the sensor may have been damaged on landing. There are plausible ways this could fail, as long as they're explained. $\endgroup$ – iAdjunct Dec 29 '14 at 17:29
  • $\begingroup$ I like the murder mystery angle... it could be that the Earth is just fine, and one of the scientists is just using the opportunity to rid themselves of one or more competitors. $\endgroup$ – GrandmasterB Dec 29 '14 at 17:37
  • $\begingroup$ @GrandmasterB: (gloved scientist to secret rival) "I made this special wreath\garland for you, Henry. Why don't you go ahead and place it near your neural centres, uh, I mean on your head, heh-heh?" $\endgroup$ – Serban Tanasa Dec 29 '14 at 18:13

I would eliminate carbon monoxide from your scenario, as (absent some source such as a lot of fossil fuel-burning engines) has an atmospheric half-life on the order of months.

I think (though I'm by no means an expert) that this is going to be true of just about any atmospheric poison. They're poisonous because they're reactive; if they're reactive they're going to degrade fairly quickly (at most months/years rather than centuries), unless there is some process that keeps replenishing them.

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To take your hazards one at a time:

  1. The carbon monoxide won't have been a problem. It's a common enough hazard that their lander would have a carbon-monoxide detector, and if CO had been present in the atmosphere at lethal concentrations (don't ask me how -- it's got a very short half-life and no large-scale natural sources), the detector would have gone off the first time they opened the door.

  2. Phosgene decomposes in water, which means it won't be globally present in the atmosphere. If it was responsible for the death, it's because someone or something broke open a storage container. The easiest way to deal with it is simply to duck back in the lander and hope a rainstorm comes by in the next few days. If they need to wait longer for the rain, they could try setting up a wet scrubber (bubble outside air through a tank of water); note that this produces hydrochloric acid as a byproduct, so they'll need to discard the water when they're done.

  3. I don't believe lipopolysaccharides can survive the digestive tract or pass through the lungs into the bloodstream. Environmental exposure is essentially a non-issue -- if you tried hard enough, I suppose you could introduce toxic levels through a cut, but that's about it.

There's a fundamental problem with your scenario: the vast majority of hazardous chemicals, especially gasses, are hazardous because they react readily with common substances (usually water or oxygen). That same reactivity means they don't tend to linger in the environment. If you want to render the Earth temporarily uninhabitable, your best bet is to contaminate the soil with something that presents a hazard from long-term exposure rather than short-term exposure (the dose builds up in the body over time), since such a substance will tend to break down on a scale of centuries rather than months.

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  • $\begingroup$ What kind of substance would do that? $\endgroup$ – ArtOfCode Dec 30 '14 at 10:41
  • $\begingroup$ My first choice would be organomercury compounds. Lead and arsenic are also good options. All of these kill over the course of months rather than minutes. If you want to be particularly nasty, a lethal dose of dimethylmercury can be absorbed through the skin in seconds, but it will take months to kill. $\endgroup$ – Mark Dec 30 '14 at 10:51

"Simple" solution considering they have a hefty generator and are on earth...

Seal off a building, pump out as much of the current air as possible, pipe in water, and run electrical current through it, cracking it into hydrogen and oxygen.

Downside, they have a lot more hydrogen in the air. That should be survivable, but not good for health. Fortunately hydrogen rises, so they should be able to vent it out of the top of the building.

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  • $\begingroup$ Downside: the slightest spark will set off a cataclysmic explosion. Electrolyze water, and your breathing air is now an ideal mix for hydrogen/oxygen combustion. $\endgroup$ – Mark Jul 9 '19 at 2:16
  • $\begingroup$ Yes, but if you're in a rush to get breathable air, it should work as a stopgap long as you're not sparking anything while getting up something more viable. In the scenario the OP put down, it's an emergency situation, which means acting quickly using available resources. Filters, antidotes, and other things mentioned here all require tools and resources they may not have. Although their ship likely had filters, there's no guarantee they're the right kind to filter out the poison. Filters are not a 'one size fits all' item, and different filters clean different things. $\endgroup$ – liljoshu Jul 15 '19 at 19:52

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