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In my story, humans colonize Titan, the moon of Saturn (for religious reasons). While complete terraforming is out of reach, they decide to try and make the atmosphere (which is already similar to Earth’s) breathable as part of the colonization process, and build a large number of devices across Titan’s surface to quickly dispense large reserves of oxygen into the atmosphere and later regulate said atmosphere to keep it breathable. The idea is that once colonists have increased the temperature on Titan to a survivable level (through other means) and figured out some way to mitigate the extreme quantities of liquid and gaseous methane found on Titan, they would turn on the dormant devices and start breathing. However, these devices are “accidentally” triggered before any of this happens, causing Titan’s atmosphere to be continuously supplied with oxygen with the atmosphere and surface still coated with flammable methane. One rogue spark leads to the entire moon erupting into flames, dooming the colonists.

Is this scenario in any way feasible? It has thematic value in my story, but seems too simple to work. Would having large amounts of oxygen on Titan cause this kind of destruction?

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  • $\begingroup$ According to Wikipedia, while there are methane & ethane clouds, "Titan's atmospheric composition is nitrogen (97%), methane (2.7±0.1%), and hydrogen (0.1–0.2%), with trace amounts of other gases". Adding oxygen waters down those percentages further so it's not clear that there's enough combustible gases for an actual explosion. $\endgroup$ Jan 14 at 20:39
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To detonate the whole Titan you would need to accumulate enough oxygen to combust a good amount of the methane present there.

I think it's hardly possible for free oxygen to be present in an atmosphere full of methane without reacting with it before you manage to accumulate enough of it. And this will happen as a slow oxidation of the available species.

On Earth something similar happened with the so called Great Oxidation Event

The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen Catastrophe, and the Oxygen Crisis, was a time interval when the Earth's atmosphere and the shallow ocean first experienced a rise in the amount of oxygen. This occurred approximately 2.4–2.0 Ga (billion years ago), during the Paleoproterozoic era. Geological, isotopic, and chemical evidence suggests that biologically-produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed it from a weakly reducing atmosphere practically free of oxygen into an oxidizing atmosphere containing abundant oxygen

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  • $\begingroup$ Would it be more likely for a more rapid, violent combustion effect to occur over a smaller area, or would the oxygen expand through the atmosphere too quickly? I’m looking for less of a giant explosion and more “fire everywhere for a decent period of time,” which probably is less feasible. $\endgroup$ Jan 14 at 22:11
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It takes more than an oxygen release to cause doomsday

Where is Titan's methane ?

With the current temperatures, Titan's methane acts like Earth's water. There's no actual coating everywhere, sometimes there is rain of liquid methane.. which would pose a risk.. but the atmosphere has 2.7% methane. There are possibly oceans of liquid methane, as well as stock of methane inside Titan. Wiki describes these possibilities:

  1. "Energy from the Sun should have converted all traces of methane in Titan's atmosphere into more complex hydrocarbons within 50 million years—a short time compared to the age of the Solar System. This suggests that methane must be replenished by a reservoir on or within Titan itself.[51] The ultimate origin of the methane in its atmosphere may be its interior, released via eruptions from cryovolcanoes.[52][53][54][55]"

  2. "Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes (that were then in winter), several large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole.[89] Based on the observations, scientists announced "definitive evidence of lakes filled with methane on Saturn's moon Titan" in January 2007.[90][91]"

https://en.wikipedia.org/wiki/Titan_(moon)

See also this savant commit on Quora. Only a small part of Titan's methane wile be exposed to the oxygen you release.. the part that is in the atmosphere.

ad 1. Cryovulcanic explanation

Current CH4 content in Titan's atmosphere is 2.7% and that will not be sufficient to do any immediate harm, when the oxygen is released. There is no surface coated with methane, the methane is released by vulcanism. Of course, the event would be disastrous when the eruption happens too near to a settlement. With all that oxygen around, you'd get baked. But the oxygen will not easily penetrate into a volcano, against its upward pressure. The gas is pushed out and ignited.

When the methane would originate from inside Titan, there is persisting danger when you release oxygen. The amount of methane is huge, when it can escape at will, you can't do oxygen-based terraformation at all, because the oxygen will be consumed immediately.

ad 2. Polar methane-oceans

Suppose all methane we see in Titan's atmosphere originates from Titan's polar oceans. In that case, it would be very stupid to attempt to terraform it early. You'd increase surface temperature on Titan and evaporate all these valuable methane oceans, before you can harvest them. When the machines that inject the oxygen are accidentally turned on, the oxygen could reach the poles ! a spark of lightning will suffice to ignite the oceans.

But don't panic, Titan is big.. suppose these polar regions only house automated mining facilities, the human colonists living near the equator can only enjoy the fireworks (their children will) but they would loose their valuable CH4 resources and their precious oxygen goes up in smoke. It would be the end of the colony, without the methane profits, why stay there..

Climate change

Releasing the O2 into the atmosphere will cause the methane to be replaced by CO2 and water vapor. As CO2 is less effective as a greenhouse gas compared to methane, expect to loose some of your temperature gain on the long term. Titan will get colder.

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  • $\begingroup$ I was under the impression that Titan had a methane cycle, much like Earth’s water cycle, and that much of Titan’s surface was “muddy” with methane in its surface. I thought there would be enough to cause a decent amount of fire and explosions in mining facilities, etc., at least in a small area. The process is not triggered intentionally/in the best interest of the colonists. $\endgroup$ Jan 14 at 22:07
  • $\begingroup$ Following up: am I correct in gathering that the event be more likely to occur if timed with a cryovolcanic eruption in the same area? $\endgroup$ Jan 14 at 22:15
  • $\begingroup$ @Neutralmouse01 you'd need a propagation of the ignited fire. When the soil has methane too, it could become a peat fire. It would depend on the amount of oxygen released. You can only burn so many methane molecules.. dependent on the oxygen your machines will add.. maybe you could give us some numbers there.. how much oxygen is accidentally produced and released ? And what would be the temperature at the time.. because the atmospheric percentage will not suffice, you'd need a giant amount of oxygen to let your moon actually explode. $\endgroup$
    – Goodies
    Jan 14 at 23:01
  • $\begingroup$ A cryogenic eruption will release the methane under high pressure, in gas or liquid form, in a very high concentration. When there is oxygen, a cloud on fire would cause havoc. $\endgroup$
    – Goodies
    Jan 14 at 23:04
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You have an example here on earth. We are actively adding methane to the atmosphere, and to an extent, it accumulates.

Atmospheric processes remove the methane from the atmosphere by combining it with oxygen.

According to Wikipedia:

If it is not destroyed in the troposphere, methane will last approximately 120 years before it is eventually destroyed in Earth's next atmospheric layer: the stratosphere. Destruction in the stratosphere occurs the same way that it does in the troposphere: methane is oxidized to produce carbon dioxide and water vapor.

The rate on Titan could be slower due to lower solar radiation.

According to //www.crossco.com:

In concentrations of 0-5% Methane in air, the mixture is too lean to ignite or burn. Methane concentrations between 5% and 17% in will support ignition and are considered highly flammable. At levels above 17%, the atmosphere is too rich for the methane to ignite.

The mixture of oxygen and methane is only explosive over a narrow range of gas concentration. I know this is not necessarily definitive, but methane in the 0-5% range will not burn in 20% oxygen.

You would need to get the oxygen concentration quite high. Before there was the big, civilization-ending fire, there would be smaller combustion events where the concentration of oxygen was locally higher. These local events would allow the terraformers to see the error in their plan, and change it.

IMO, your situation falls short of plausibility.

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