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Whenever a lander enters an atmosphere, it generates a lot of friction and that heats up the heat shield. On Earth we have seen videos of spacecraft with red-hot shields.

On Saturn's moon Titan, wouldn't the ignition of some of those hydrocarbons kick-start a run-away inferno?

How can fast moving meteorite not do the same?

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    $\begingroup$ It's not friction that generates heat, it's mostly compression heating as far as I remember... $\endgroup$
    – Mołot
    Mar 7, 2016 at 12:04
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    $\begingroup$ In truth, Earth is the weird planet. Most planets don't have readily available supplies of an oxidizer in their atmospheres. You're not going to "burn" methane without an oxidizer, such as oxygen. If Titan's atmosphere did have plenty of free oxygen, it wouldn't have a methane atmosphere - if it evolved similar to ancient Earth, it would most likely have a mix of water, carbon dioxide and oxygen. $\endgroup$
    – Luaan
    Mar 7, 2016 at 12:54
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    $\begingroup$ If this were a real risk, the first meteorite to come along would have caused it ... $\endgroup$
    – pjc50
    Mar 7, 2016 at 14:17
  • $\begingroup$ Is it possible for another atmospheric component other than oxygen to act as an oxidizer? $\endgroup$
    – Gabriel Fair
    Feb 18, 2018 at 1:09

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In order for a combustion process to happen, you do not only need fuel, you also need an oxidizer. On Earth, that is usually the oxygen in the air. In Titan's atmosphere, there is no oxygen. This applies to other atmospheres too, like the hydrogen dominated atmospheres of Jupiter and Saturn. Hydrogen, just like the methane in Titan's atmosphere, is flammable too, but only in the combination with oxygen.

Basic check, the fire triangle:

fire triangle

For a meteor impacting Titan:

  • Fuel: YES
  • Heat: YES
  • Oxygen: NO
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    $\begingroup$ Just to add: it would be virtually impossible for any planet or moon to sustain an atmosphere containing significant quantities of both oxygen and hydrocarbons for very long. Sooner or later ignition would occur and after the explosion the body would then be left with a very boring atmosphere of carbon dioxide and water vapour. Alternatively if oxygen and hydrocarbons were building up slowly in an atmosphere, they might react unspectacularly through slower noncombustion reactions (UV catalysed for example) before they got to the concentrations that could cause ignition. $\endgroup$
    – Level River St
    Mar 6, 2016 at 23:12
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    $\begingroup$ Though we should note that any outside observer would conclude that Earth has a very unusual non-equilibrium atmosphere with an enormous concentration of oxygen. $\endgroup$
    – Mark Adler
    Mar 6, 2016 at 23:43
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    $\begingroup$ @MarkAdler Earth's atmosphere is perfectly stable with respect to reactions with itself; biological activity removes carbon and sequesters it (ultimately as oil/coal/natural gas.) It'd be interesting to see what "weather" we had if there were huge periodic releases of methane capable of producing vast explosions, potentially more dramatic than forest fires. Europa has mostly O2 atmosphere from the reaction 2H2O --> O2 + 2H2 (H2 lost to space as molecular velocity exceeds escape velocity) but that mechanism wouldn't work for Earth so Earth's O2 rich atmosphere would indeed stand out as unusual. $\endgroup$
    – Level River St
    Mar 7, 2016 at 1:46
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    $\begingroup$ To follow up on @LevelRiverSt's comment, one of the proposed strategies for looking for extraterrestrial life is to look for planets whose atmospheric spectra contain unusually high levels of oxygen. Because oxygen is so reactive, any planet with large amounts of it in the atmosphere must have some process to replenish it, which might indicate the existence of photosynthetic life. $\endgroup$
    – quanticle
    Mar 7, 2016 at 2:04
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    $\begingroup$ @PirateApp It will burn, potentially very quickly, until the oxygen in the tank is depleted. Then the reaction would stop. $\endgroup$
    – SE - stop firing the good guys
    Apr 6, 2019 at 13:25

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