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Name: David P.
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A


Question:
One of Saturn's moons has liquid methane lakes and methane gas clouds. Can this gas be ignited causing a giant explosion? Such as from a lightning strike or a meteorite?


Replies:
David,

I do not know if you remember the Jupiter - Shoemaker Levy 9 collisions back in 1994.

http://www.youtube.com/watch?v=DgOTcIfU75Y&NR=1&feature=fvwp

Note that Jupiter is a gas planet composed mostly of the flammable H2 gas (liquid and solid probably in the inner core). The video shows massive explosions and black marks on the planet for months - but the entire planet did not burn. Why?

From the perspective of chemistry, combustion (or ignition) is nothing more than a chemical reaction (that produces a lot of heat) wherein the "fuel" (in this case, methane) combines chemically with an oxidant (usually, but not necessarily, oxygen), under conditions where some initial energy (think of the necessity of striking a match before it can burn) is supplied.

So, we need: fuel, oxidant, ignition energy or conditions.

We know we have the fuel (methane). I'm not sure what the ignition energy requirements are for methane at the temperatures and pressures of Saturn's moons, but we could assume that a meteor strike would supply enough such energy and if there is a spark, could cause ignition - much like it did on Jupiter.

However, I am not sure that there are oxidants on Saturn's moons, or on Jupiter. From what I remember, the moons and many of the outer planets have "reducing atmospheres" - which means that there is a lack of oxygen or some such oxidant - which allows highly energetic compounds like methane and ethane to exist in the first place. If oxygen were present, we would more likely find CO2 because, even though no ignition takes place, small oxidation reactions can and oxidize (as oppose to reduce) the methane to CO2.

So, yes, a meteor can cause ignition, but, no, the entire planet (Jupiter) or moon (Saturn) will not explode because there is not enough oxidant present to keep the fires burning. The explosion we saw in Jupiter was essentially due to the high energy plus whatever oxidant was present from the comet/meteors, and the little in the surrounding regions of the impact.

Greg (Roberto Gregorius)
Canisius College


No, I doubt it, Titan is the moon in question, but the liquid methane is far too cold.

Sincerely

David H, Levy


Highly unlikely. The combustion (detonation) of gases such as methane requires the presence of oxygen to burn (or explode). A fire requires three components: 1. A fuel, 2. An oxidant, 3. An ignition source. Remove one of the three, and no fire occurs.

Vince Calder


David

I saw the same program and wondered about the same thing, but such a giant explosion would require a lot of oxygen. Here is the chemical reaction formula for burning methane:

CH4 + 2O2 => 2H2O + CO2
From

http://wiki.answers.com/Q/What_is_the_chemical_equation_for_methane_burning_ in_oxygen

So you have to have 2 molecules of diatomic oxygen to each molecule of methane.

They did not say anything about how much oxygen there was on that moon and it is still there.

Sincere regards,

Mike Stewart



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