Can a Match Light on Mars?

[CardinalBiggles]

Is there sufficient oxygen in the air (In The Well gives the percentage at 15%) at 40% of Earth pressure for fire to burn without assistance?

[jacobmuller]

GURPS Classic - Mars, pg61: "No risk of a Hindenburg style fire" suggests your answer is no.

[malloyd]

Originally Posted by CardinalBiggles

Is there sufficient oxygen in the air (In The Well gives the percentage at 15%) at 40% of Earth pressure for fire to burn without assistance?

Depends on what's in the match. This is too low by a factor of two for most things to burn vigorously - few things do below 0.1 bar oxygen. But some things will smolder, and of course some matches contain a nitrate oxidizer, those will light fine.

[Not another shrubbery]

Originally Posted by malloyd

Depends on what's in the match. This is too low by a factor of two for most things to burn vigorously - few things do below 0.1 bar oxygen. But some things will smolder, and of course some matches contain a nitrate oxidizer, those will light fine.

Even with the high CO2 to oxygen ratio?

[malloyd]

Originally Posted by Not another shrubbery

Even with the high CO2 to oxygen ratio?

I don't see why that would matter. From the standpoint of an oxygen fire, carbon dioxide is just another inert buffer gas. If you are thinking about it as an extinguisher, that works here on Earth as a physical effect - by diluting the oxygen, and to a lesser extent by pulling out heat - rather than a chemical one. You could get a similar effect by dumping liquid nitrogen on the fire, and nobody argues the high nitrogen/oxygen ratio in air is a big problem for burning things.

[Not another shrubbery]

Originally Posted by malloyd

I don't see why that would matter. From the standpoint of an oxygen fire, carbon dioxide is just another inert buffer gas. If you are thinking about it as an extinguisher, that works here on Earth as a physical effect - by diluting the oxygen, and to a lesser extent by pulling out heat - rather than a chemical one. You could get a similar effect by dumping liquid nitrogen on the fire, and nobody argues the high nitrogen/oxygen ratio in air is a big problem for burning things.

I'm way out of my depth, but I thought that the lower oxygen partial pressure would be a big factor. I was reading the limiting oxygen concentration article on Wiki, and it seems to say that CO2 is more effective in that regard than nitrogen.

[Anthony]

Originally Posted by malloyd

You could get a similar effect by dumping liquid nitrogen on the fire, and nobody argues the high nitrogen/oxygen ratio in air is a big problem for burning things.

Sure they do. Stuff will burn in 0.2 atmosphere pure oxygen that won't burn in an oxygen/nitrogen atmosphere. Inert buffer gases suck up heat, preventing combustion from continuing by preventing the gas mixture from getting hot enough.

The reason you use CO2 for fire extinguishers rather than nitrogen is that (a) CO2 is a lot easier to store, and (b) CO2 is a bit denser than air.

[sir_pudding]

Originally Posted by jacobmuller

GURPS Classic - Mars, pg61: "No risk of a Hindenburg style fire" suggests your answer is no.

Transhuman Space Mars has a lot more oxygen than real Mars. People with no more than Filter Lungs can breath it.

[RyanW]

Old topic is old, but 15% oxygen at 0.4 atmospheres is an oxygen partial pressure of 0.06 atmospheres (only slightly lower than the "dying of asphyxiation, but slowly" range that Everest climbers who go without bottled oxygen face). Since Everest climbers use cook stoves during ascent, I imagine that you can get a match to burn, though it could be difficult. For fire starting, I bet matches with a crystalline nitrate (probably of ammonium or potassium) would be commonplace, which would strike (though not continue burning) even with zero atmospheric oxygen.

Incidentally, 0.16 atmospheres partial pressure of oxygen is the medically suggested minimum for long term exposure. The existence of Lhasa, La Paz, and similar cities demonstrates that this isn't a hard limit.