Recent evidence shows that there is alot of methane being generated on the planet Mars. Sometimes there can be a plume of 19,000 tons of methane. Methane can be associated with biological or geological processes. This methane is destroyed quickly when it reaches the surface because the Martian surface is very hostile to organics. But it always is regenerated by some unknown process occurring in the planet's interior. I'm not sure that you can tell the difference between bio methane and geo methane. Whatever the origin of the methane it could be very useful to human explorers who try to colonize Mars. Imagine trying to cook with the stuff.

I thought Mars was too cold for humans to survive.

Methane>Heaters>Heat?

Methane + Oxygen > Heaters > Heat

If you're being pedantic, Methane + Oxygen > Heat > Heaters.

Kim Stanley Robinson uses Hydrazine for his motors in his books, along with solar power. I suppose oxidation is out, because of the scarcity of oxygen and it's use for breathing. Though, I don't ever remember him mentioning methane at all. Nitrogen is the element they are always looking for.