Mouthwash wrote:Source of the post (B) have some part of themselves (atmosphere, solid layer) destroyed by a chain reaction?
All hydrocarbons have a flash point. The point where a substance can ignite or explode without any external form of heating. This value is between the melting point and the boiling point.
You would think you could ignite the entire methane atmosphere of Titan with a single match strike! The problem is that no material on Titan can ever reach that flash point. For methane it's about -178 degrees C, ethane it's about -140 degrees C and for propane it's -104 degrees C. Since Saturn has a roughly circular orbit around the sun and Titan has a circular orbit about Saturn, Titan's surface temperature will never deviate much from about -179 degrees C. So, any hydrocarbon will need to be very strongly heated or have a big enough kick to get it to react. Or you could squirt oxygen into the methane atmosphere and then strike a spark.
The surface temperature of titan is well above the flash point of methane (-178C). Furthermore, we know now that at the surface, the concentration of methane gas is ~5%, this is within the explosion fraction range of methane of 5-15% on earth with an O2 conc. of 20% (the fact that we are dealing with gas at the surface actually negates the relevancy of methane's flash point).
I also suspect that because the pressure of the atmosphere at the surface is higher than at earth's surface, the explosion fraction for methane would actually slightly extend below the 5% lower limit add to this the fact that you'd be burning it with 100% O2 instead of earth's paltry 20% and this probably pushes the explosion fraction limits even wider. The fact that the gas is very cold is irrelevant. What's -180C when you're talking about a flame temperature in the thousands of degrees? Nothing.
It is quite certain that you could light a flame off of a bottle of O2 at the surface and it would self sustain 'till it ran out. Even if you are uncomfortable with the closeness to the lower limit of the explosion fraction at 5%, performing a concentration of methane out of the atmosphere to a slightly higher % would be trivially easy with a semipermeable membrane and a very small amount of energy input (the amount of entropy change you'd need to concentrate it to say, 10% would be very small). The nice thing about the ability to carry liquid O2 instead of liquid hydrocarbon is the high density. a small bottle of O2 would go a long way.
Even if you wanted to run some silly scheme of condensing the methane out of the atmosphere as a liquid using a cryo-cooling loop and then heating and burning off the purified liquid all at once (like for a rocket), this would be VERY easy and energetically inexpensive to do since you're already so close to the boiling point.