Jose Mujica

If we lived within our means - by being prudent - the 7 billion people in the world could have everything they needed. Global politics should be moving in that direction. But we think as people and countries, not as a species.

Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it's hard to make it pay off - Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap.