"The thinking used to be that astronauts were going to have bring all their water with them, but there is plenty of water on Mars," Green says. "It's weeping out of craters in the summers; there are aquifers.
"So, no, we've learned we won't need to bring all of our water. We'll bring a straw, because we know where we can go to get it."
Titan also happens to have an orbital period of 16 days (compared with Earth's 365) so humans would have some adjusting to do when it comes to the workday. And oh: Temps also average about -179.5 degrees Celsius. So. Bring some sweaters.
"If you're looking for more of an ocean world," Green muses, "it would be Europa."
A moon of Jupiter, Europa is believed by planetary scientists to have lots of water, and it may even be liquid: "The tidal forces from Jupiter could accelerate enough energy on Europa that it would literally melt its ice crust, creating an ocean," Green says.