Water can be created by burning hydrogen or by burning hydrocarbons like gasoline, but we don't really create water to drink that way. Even on Earth, we just move around the water that's here!
The same thing happens on a space mission, except that there isn't any access to rain or rivers or lakes. Astronauts must bring along the water that they need.
To avoid having to bring so much, astronauts would like to be able to purify and recycle their waste water. One way to do that is to use the water to grow plants, so you can see how many of the goals of long-term spaceflight are inter-connected.
Astronauts on the International Space Station will wash with water collected from the air itself. This is water that has been exhaled in the astronauts' breath, and sweat that has evaporated off their bodies. That sounds kind of gross, but because the water is collected in vapor form, it's actually pretty clean--like rainwater! Other wastewater will be purified by filters for drinking and other uses.
Water is very heavy, which makes it expensive to launch it into space. Each drop that can be reused in orbit is important!
Page last updated on June 24, 2015.