[X] My Assistant

[edstrick]

My understanding -- it may be wrong -- is that once you get it going, magnesium will happily burn in a nitrogen atmosphere. Supposedly, the white "ash" from burning magnesium in air is partly magnesium nitride.

[djellison]

I've never tried to put it out with a CO2 extinguisher - but I did demonstrate the (at a first level) unintuitive concept of CO2 puting out a burning splint but making burning Magnesium burn brighter to some younger students at school using a tank of the stuff a bell jar and an asbestos mat

Doug

[edstrick]

One thing I'm SURE of.... it won't burn in argon.

It MAY be Titanium that burns 21% oxide 79% nitride, not magnesium.

Factoids are those bits of information stuck in the folds of your grey-matter that just sort of fall out of the gaps when you bang on your head.

[Juramike]

Flourine will burn impressively well in a hydrogen atmosphere to produce HF.

This might be handy at a future barbeque on/in Jupiter. (No glass bottles please).

[helvick]

Apart from the already poisonous ambient atmosphere and 2.5g local gravity while floating in the Jovian cloud tops that HF exhaust definitely makes that one BBQ I'll have to pass on. The view might be pretty cool though.

[Stephen]

I remember that somebody (Arthur C. Clarke?) once wrote a story where the recently proven existence of such high-temperature runaway oxidation on Earth was considered the clincher in proving that the planet was uninhabitable by Martian astronomers.

Sounds like Clarke's tongue-in-cheek essay "Report on Planet Three" (which can be found in the 1972 collection "Report on Planet Three and Other Speculations").

======
Stephen

[nprev]

Good old Arthur C....how's he doing these days, anyhow? He wrote some of the most memorable & significant things in SF. It's a shame that we haven't seen anything new from him for awhile, but he is getting on in years...

Well, to redirect this discussion back to its original theme somewhat, I think that 'fire' is indeed probably a phenomenon restricted to worlds with an extensive biosphere. Although we only have one example to work with, life seems to be unique in the sense that it's generally anti-entropic, and actually causes a general energy imbalance in the local environment (i.e., free oxygen). This imbalance is of course crucial for maintaining living processes, but also can lead to runaway chemical reactions like fire.

What's interesting is that worlds that may harbor micro-environments favorable for life (like Mars) apparently do not exhibit a general entropic imbalance. Conversely, Europa is locked in a shell of ice and possibly may have a global habitable environment underneath, yet highly energetic reactions like fire just don't happen underwater. Perhaps the original question here should be constrained to considering only planets with extensive atmospheres...

[tty]

I agree - a high oxygen atmosphere is probably an excellent indication that there is life on a planet, and what is more, photosynthetic life or a reasonably close analogue. However the absence of oxygen does not prove the absence of an extensive biosphere. Our one example may have had an high-oxygen atmosphere for less than 25 % of the time life has existed here, and almost certainly for less than 50 %.

[nprev]

Excellent point, tty; anerobes rule!

Come to that, an oxygen-enriched atmosphere is really a very limited indicator, albeit an apparently unambiguous & quite detectable one. O2 allows high-energy organisms (and fires) to exist, but who's to say that a largely chemosynthetic rather than photosynthetic biosphere would not be equally viable or complex?

We know nothing yet, really...hope to live long enough to see some answers!

[JRehling]

[...]

[Juramike]

Another angle to this would be that you could potentially, on a lifeless planet, have a big fire (in O2, Fl2, or Cl2)... once. If some quirk of, let's say, the introduction of a hitherto trapped reservoir in the crust or in oceans made it's way to the atmosphere, you could get a single catastrophic burn-off that would last until the chemical energy were exhausted, and then end, forever.

Actually, you might get away with it more than once. The terrestrial analog would be a gas vent (petroleum, natural gas, methane in a swamp) lighting up in the oxygen atmosphere. It vents, it burns for a while, then burns itself out.

If there was a geochemical process that could regenerate the key reactive species (I haven't a clue how fluorine gas could be (oxidized?) back down to F2 geochemically), this whole process could repeat itself ad infinitum. All without having to invoke biology.

I would not be suprised to find that some very funky sulfur redox chemistry is occuring on Io right now, possibly involving generation of a flame somewhere in the cycle.