Well, here it's much easier and safer to use fossil fuels. But our space shuttles are powered by liquid Hydrogen and Oxygen.
If you have water, you can split it into 'H's and 'O's and those burn like crazy.
On Mars there's no atmosphere so I don't think we could actually cause global warming. If anything we'd cause the creation of an atmosphere...
WHAT!!???
There is an atmosphere on Mars. However, the moon has very little atmosphere.
Oh and I don't remember enough chemistry to explain why using water/ice as fuel is efficient, I just know that since they've been talking about colonizing the moon and finding water on Mars they've been mentioning fuel as a use for that ice.
The other benefit of launching from the Moon being the weaker gravity thus requiring much less fuel.
__________________
From the SigmaTo the K!
Polyamorous, Pansexual and Proud of it! It Gets Better