In my setting, a permanent "fog" hangs over the ocean. It is thick, granting low visibility to anyone within it. Instead of water droplets, however, this fog would consist of some substance or combination of substances, that is/are able to be harvested for, and if necessary refined into, fuel (and ideally other materials, such as plastics).

The "fog" should have the following properties:

  • It exists as a heavier-than-air gas or cloud of fine droplets at sea level (temperature is open for discussion, but I would prefer an ambient temperature around 5-10°C for the sake of the rest of the worldbuilding);
  • It is translucent, granting low visibility, equivalent to or less than that of a thick real-world cloud fog;
  • It is usable as a fuel, or can be refined into such a form via relatively simple processes;
  • It is plausible for the substance to exist in an earth-like atmosphere/biosphere.

The question: what material would plausibly display these properties? I'm aiming for plausibility - closer to science fiction than science fantasy.

I hope that my question is clear enough, and suits the site!

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Aug 30, 2019 at 11:25

6 Answers 6


Manna from... sea spray?

This is a super cool question, and entirely feasible within the realm of . The secret ingredient in such an atmosphere is going to be sea spray!

Oceans are already foggy[citation needed] due to two related processes: midair condensation and droplet injection. Midair condensation happens when warm, moist air cools below the dew point and begins to form droplets of water suspended in the air as the Brownian motion of the air molecules outweighs the tendency to stratify by density. Droplet injection is a mechanically-intensive process that requires something to put energy into aerosolizing the seawater (or gasoline, or cheese).

In the ocean, especially near shore, these processes are related because the dew point is determined by humidity - and droplet injection increases the relative humidity of an area. On coasts, the mechanical effort to aerosolize the seawater comes from breaking waves. Every time a big, rolling wave comes through and white water is visible in its crest, you can be sure it's leaving behind a trail of suspended water droplets. These droplets often stay suspended long enough to spread inland and cause fog formations. This process also occurs in the open ocean when the wind is strong enough to cause whitecaps, which have the same effect as breaking waves.

However, water isn't the only thing in the ocean[citation needed] and sea spray isn't pure water. Rather, it's a collection of salts and organic matter and little microorganisms that happened to be caught in the breaking wave. This means that ocean fogs are incredibly complex micro-ecosystems that we still don't know a lot about.

The problem as posed in the question, therefore, is how to manipulate the environment to maximize the concentration of organic materials (ideally hydrocarbons) in the surface ocean, so that sea spray, and therefore fog, will be especially valuable.

Worldbuilding ideas


On the highly-realistic - but less effective - end of the spectrum, we can manipulate normal Earth biology. The best option here will be microalgae, which are already found in seawater in high concentrations. If we can get lots of microalgae into the air, the resulting fog will be highly valuable not just as a fuel source, but also for food and other important natural compounds. Phytoplankton already have a tendency to "bloom" when conditions are right, during which time their concentrations increase by a factor of 100-1000x. These blooms are so dramatic that they'll discolor the surface ocean and be visible from space:

Phytoplankton bloom from NASA's Earth Observatory, accessible at https://earthobservatory.nasa.gov/images/44478/phytoplankton-bloom-off-iceland

In order to make the sea-spray fog worth harvesting, however, the blooms will need to go beyond natural occurrence. Fortunately for us, humans have been conducting large scale nutrient fertilization experiments near the outflow of each of our rivers for some time now. Such man-made blooms can reach truly disgusting concentrations, as China faced while preparing for the 2008 Olympic games. Such intense concentrations of algae, combined with large waves, could easily make fog worth harvesting for fuel.

Oil slicking

On the more-disruptive side of ocean-engineering, we could deliberately add the useful compounds directly to the ocean surface. In fact, humans already tried this (albeit for different reasons) resulting in one of the largest oil spills, and deliberate oil dumping continues to be a huge problem in many places.

On a world where the ocean surface is covered in hydrocarbons, it's likely that the fog would be largely hydrocarbon-based as well. This could be the result of leaking natural deep-sea oil wells or pentane seeps, or something more exotic and biological like mid-ocean ridge bacteria that produce rocket fuel as a way to avoid nitrogen toxicity.

The trick here would be balancing plausibility of the oil layer thickness against the relative proportions of oil and water in the air. The thicker the layer on the surface, the more oil in the sea spray, but also the more disruptive and implausible the oil slick. Fortunately, hydrocarbons are immiscible with water, so separating the two should be simple enough even if collected together.

Ethanol oceans

On the far end of implausibility, it's possible to imagine the oceans themselves consisting of fuel. Ethanol and methanol oceans have been discussed before on this site, but this seems to go against the sentiment of your question; it'd be much easier to simply collect the fuel from the ocean. Unless, of course, the ocean was inaccessible for other reasons...


Having an ocean produce fuel naturally is a terrifying idea on any planet in which ignition sources also exist. Fuel-based sea spray is basically gasoline immediately before ignition, and equally flammable. As awesome as a novel would be that begins with humans setting a nearby planet on fire from their chemical rocket landing, I must urge caution if you'd like the inhabitants of said planet to remain alive for very long. Fuel sources requiring some refinement or distillation prior to use would be much more useful.

Additionally, collecting fuel from sea spray is difficult to justify when there's a much more concentrated source nearby in the form of sea foam. Sea foam is essentially distilled sea spray, with an incredibly high organic carbon content and lots of other goop. Collecting this would be as simple as walking along the beach with a vacuum cleaner, maybe with one of those screens on the front to avoid sucking up all the sand as well.

Good luck!

  • 1
    $\begingroup$ This is a really informative and creative answer, thanks! I'm already in love with the Phytoplankton idea. The idea of microalgae suspended in the fog vs. or alongside hydrocarbons is great. I wonder, however, why would the people bother harvesting the ocean spray, if they could simply harvest the water containing the algae? $\endgroup$
    – fercley
    Aug 28, 2019 at 21:54
  • 1
    $\begingroup$ @fercley Glad it's helpful! Honestly, not harvesting the ocean water or sea foam directly was the biggest challenge with this answer. It's imaginable that the ocean is hard/impossible to access, or contains things with lots of teeth, or is toxic for other reasons. Alternatively, the sea spray may be easier to process - maybe the algae cell walls are broken down in the aerosolization process, or there's a certain distance inland where the water fog has precipitated out but the organics remain volatile for a longer time so the fog is more concentrated. $\endgroup$
    – Dubukay
    Aug 28, 2019 at 22:09

How about a rising column of gas, rather than a fog?

Your ocean contains swarms of a yeast-like organisms which "fart" a fuel gas out into the water as they feed. The gas, once released, bubble up to the surface and then being lighter than air, rise up and away.

Harvesting can thus best be achieved by capturing the gas right above the surface, before the winds disperse them beyond usefulness.

  • $\begingroup$ This is a nice idea, actually. Are there any such gases that would be visible, and resemble a fog, that you're aware of? Most of my immediate thoughts for fuel gases are transparent, even in large volumes. $\endgroup$
    – fercley
    Aug 28, 2019 at 21:34
  • $\begingroup$ I just provide "out of the box" thinking. I lack the scientific credentials to actually identify specific gases. I seem to remember some swamp gases being pretty explosive. Maybe some of them have color and opacity. I am sure that other, better schooled members of this forum can provide some ideas. If all else fails, the organisms could produce a mixture of two gases... one that burns and another which has your desired aesthetic. $\endgroup$ Aug 28, 2019 at 21:40

This question reminded me about the black sea. It has a has a habitable upper layer and a dead bottom layer. Source

As previously mentioned, biomass consumes oxygen as it decays. When there is no more oxygen, this biomass continues to decay, leading to the consumption of sulfates by the bacteria and the production of hydrogen sulfide (H2S), a highly toxic gas. The permanent stratification of the Black Sea acts as a lid over the deep waters, in which this hydrogen sulfide has accumulated and reaches now unprecedented concentrations.

This H2S can be spilled e.g. by asteroids or nuclear explosions. Or it just might get too much in the future and spill over from itself.

H2S is denser than air at above c.a. -10°C temperatures.

It can be used as fuel or converted to hydrogen. But it is poisonous to humans, so your sailor-fuelminers have a dangerous job.


How about ammonia? According to Wikipedia, Jupiter’s visible clouds are made from ammonia and water. It can be used as fuel as well. Although it would have to be frozen in crystal form to be opaque, as it is on Jupiter. So it’s not bulletproof.

Another possibility is hydrogen sulfide. Unfortunately hydrogen sulfide is colorless, but I have a workaround: ammonium hydrosulfide (which also occurs on Jupiter and contributes to its red color). It takes the form of a yellow-orange fuming liquid at room temperature and could be refined to H$_2$S and used as a fuel. As an extra bonus, it could also be refined to ammonia to be used as fuel as well.


Fortean rain.

I am reading the Book of the Damned by Charles Fort. People are familiar with rains of fish and frogs (which continue to this day!) but other stuff comes down sometimes.


That, March, 1832, there fell, in the fields of Kourianof, Russia, a combustible yellowish substance, covering, at least two inches thick, an area of 6oo or 700 square feet. lt was resinous and yellowish: so one inclines to the conventional explanation that it was pollen from pine trees-but, when torn, it had the tenacity of cotton. \Vhen placed in water, it had the consistency of resin. "This resin had the color of amber, was elastic, like India rubber, and smelled like pre­pared oil mixed with wax."

Rather than coming up from the ocean, this stuff falls from above. The recurring question in Fort's works is where these sky falls come from - his proposition is that there are unseen realms above us or perhaps in the solar system around us that contain things and these things can rain down.

Realms in the sky is pretty zany but fall of carbonaceous stuff from space is not zany. Fort has a whole category on "coal from the sky" which at the time he was writing was categorized with fish and frogs from the sky as picked up from earth by wind and redeposited elsewhere - meteorites were thought exclusively made of metal or stone. But it is now recognized that there exist carbonaceous meteorites which seem coal like in their composition.

A fine candidate for your fog would be a rain of Tholins: reddish-yellow carbonaceous materials which are widely distributed around our solar system. Tholins are thought to be responsible for the reddish haze around Titan.

An aspect of Fortean rains is their extreme locality. One would expect stuff coming from space (or stuff transported by whirlwind a great distance) to be distributed widely but general that is not the case for Fortean rains which is why he invokes invisible realms not that far from the earths surface.

This stuff can dissolve into the water or sink, so collecting it from the ocean is not practicable.


1: Unless you too invoke invisible realms above the ocean there is no good reason this stuff should only fall over the ocean.

2: This is carbon, which it has to be because you want to use it for fuel. A finely distributed fog of tiny flammable particles presents a tremendous explosion risk, akin to a grain elevator or coal dust explosion. A lightning bolt would turn the entire area into a fireball. You could probably see the wall of flame coming (especially at night) and then hide in the hold of your ship and ride it out. When it went out there would not be oxygen left in your locality for a few minutes. Maybe an fire event of this sort is what ends the rain and the harvest every time, and the collectors count on being able to see it coming and hide in the hold.

I think you should have the fogs of this stuff come periodically, not constantly. When they come the boatmen go out (with masks on) and collect it with big nets. No smoking.


Hydrogen peroxide

Recently it was discovered that microscopic droplets of water spontaneously produce hydrogen peroxide and that hydrogen peroxide was not lost when the microdroplets recombined into bulk water. Thus it is theoretically possible to collect the dew and refine the peroxide from water. It is potent oxidizer with wide application in chemistry, even as explosives/rocket propellant.


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