Burning Titan, An ahmosphere on fire Options

[Spirit]

Is it possible to light the atmosphere of Titan. I think that the methane could burn. What will happen if we set a fire on Titan? Will the atmosphere burn and melt down the water ice?

[Toma B]

Yeah!!! Ka-Booom!!!! Titan explodes!!!
All you need is to light a match!!! That and some oxigen ( maybe few trilions of tons..)
But if you think that would be some explosion think how big BOOM will be if you light a match on Jupiter...90% of its mass is Hydrogen...
Nice idea...but something's missing...

[Guest_BruceMoomaw_*]

Yeah, we've discussed this before. You can't set Titan on fire without oxygen (or it would have burst into flame at the first meteorite impact!)

But it has been pointed out that you can run a gas burner on Titan by doing the exact reverse of what a gas burner does on Earth -- that is, instead of squirting methane into an oxygen atmosphere and then striking a spark, you squirt oxygen into a METHANE atmosphere and then strike a spark. And this could even be used to provide the internal heat for a space suit on Titan (which would also be unique in not having to be pressurized like the space suit necessary on the surface of any other world in the Solar System).

[ljk4-1]

Don't be giving any future teenage Titan explorers any ideas!

[ugordan]

But it has been pointed out that you can run a gas burner on Titan by doing the exact reverse of what a gas burner does on Earth

Would that actually work? The concentration of methane in Titan's atmosphere is vastly lower than the concentration of oxygen in Earth's atmosphere. Consider this comparison: methane on Titan is roughly present in the same percentage as water wapor in Earth's atmosphere. Now, take pure sodium metal -- it reacts violently with water, releasing hydrogen that often ignites due to the heat released (but that's beyond the point). If you leave a piece of sodium lying around (it's usually stored in petroleum!), exposed to air, you don't actually see it burn or violently oxidate. Slowly react -- perhaps, burn -- no.

My point is that sustained burning on Titan the way you described seems improbable, considering also the fact the actual methane there is at crygenic temperatures.

[angel1801]

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.

The problem is that no material on Titan can ever reach the flash point.

For methane it's about -170 degrees C, ethane it's about -140 degrees C and for propane it's -104 degrees C.

Since Saturn has a roughly scircular 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.

[deglr6328]

I think angel's reasoning, while interestig, may be a bit off. The surface temperature of titan is actually well above the flash point of methane (-178C vs. -223C). 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 semipermiable 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 cryocooling loop and then heating and burning off the purified lquid 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.

[Guest_BruceMoomaw_*]

You've just exactly redescribed the scheme Robert Zubrin proposed a few years ago in (I believe) "Analog".

[deglr6328]

never read anything by Zubrin but certian possibilities about space are just begging to be contemplated. this is one of em I guess.

[RNeuhaus]

Yeah, we've discussed this before. You can't set Titan on fire without oxygen (or it would have burst into flame at the first meteorite impact!)

Titan has some few meteorite craters and around this must have melt ice and forms some rivers around any impact crater. The meteorite must be very hot when it enters to the high density Titan's atmosphere plus the burning flame of meteorite.

Rodolfo

[mchan]

The heat from atmospheric friction would be carried off by boil off of the meteorite surface. Rock / ice is a fair insulator. The short time of passage thru the atmosphere would not allow for the interior of the meteorite to increase significantly in temperature. But even if the meteorite could absorb much of the energy from atmospheric deceleration, that energy would be low compared with the energy released by the surface impact.

Rivers forming from impact craters would imply some energy release sustained over time. I guess there would be no large flows.

[edit] There could be shock heating of the meteorite interior during the atmospheric passage.

[tty]

Rivers forming from impact craters would imply some energy release sustained over time. I guess there would be no large flows.

There might be. A lot of energy is deposited in the rock under and around the crater and dissipated rather slowly. Studies on terran impact crater have shown geothermal effects sustained over century- to millenial timescales. Much would depend on the characteristics of the Titanian "bedrock" of course.

tty

[Guest_Richard Trigaux_*]

The heat from atmospheric friction would be carried off by boil off of the meteorite surface. Rock / ice is a fair insulator. The short time of passage thru the atmosphere would not allow for the interior of the meteorite to increase significantly in temperature. But even if the meteorite could absorb much of the energy from atmospheric deceleration, that energy would be low compared with the energy released by the surface impact.

Rivers forming from impact craters would imply some energy release sustained over time. I guess there would be no large flows.

[edit] There could be shock heating of the meteorite interior during the atmospheric passage.

On Earth meteorite were found which were icy cold just after falling. A meteorite called of Dhurmsala (or Durmsalah, spelling can vary) which fell at the end of the 19th century 80kms north east of Dharamsalah, India, was so cold that it gave frost and make fingers dumb a quater of an hour after falling. This cold was, of course, from space (it was a light grey stone chondrite, which equilibrium temperature in space is far bellow zero). Of course, the outside layer of this meteorite burned into the air, and heat difference made the meteorite break appart, low enough into the atmosphere so that the inner blocks could no more be heated. This configuration may be relatively rare, but it proves that a meteorite is not necessarily hot when it falls on the ground.