Carrie-Anne Moss

When you play a doctor, you have to look like you can do it but you don't actually go and do it. It's not like you learn how to cut open somebody and go do surgery. You have to think of a human being and not play the idea of what that would look like.

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.