As NASA and other space agencies continue humanity’s interplanetary reconnaissance, one thing is becoming very clear: on balance, the solar system is a rather soggy place. Water, mostly in the form of ice, lurks practically everywhere we look. There are water deposits on the Moon, on Mars, and even in the cold, shadowed floors of deep polar craters on sun-broiled Mercury. Water exists in even greater abundance further out from the sun, constituting much of the crust for a wealth of dwarf planets, moons, and asteroids and even occasionally forming subsurface oceans.
Planetary scientists speak often and with great eloquence about how all this water boosts the possibility of alien life right in our solar system; much less discussed is how it boosts the possibility of carrying human life far beyond Earth. Water will be a cornerstone of our existence everywhere we go, of course, perhaps in more ways than you realize. The killer app for all that extraterrestrial water isn’t just beverages and baths—it’s also rocket fuel.