Why would a home on the Moon reuse its air and water?

Take a slow, deep breath and feel the cool air fill you up. Now think of a long drink of water on a hot day. Here on Earth, you get air and water every day without even trying.

Picture a little home on the Moon, where astronauts live and work. The astronauts clean their used air and water so they can use them many times. Why would a Moon home reuse its air and water?

Your body needs oxygen, which is the part of the air that keeps you going with every breath. Astronauts need oxygen too, every minute of the day. They also need water to drink, to cook and to wash.

Out on the Moon, there is no air at all to breathe. There are no rivers, no lakes and no rain. A Moon home cannot open a window for fresh air or fill a jug from a stream. So when the home runs low, where could more air and water come from?

They have to come all the way from Earth. Every tank of oxygen and every bottle of water rides up on a rocket as cargo, which means the things a rocket carries.

A rocket can lift only a little cargo, because heavy things need a huge amount of fuel to leave the Earth. Water is heavy, and astronauts drink and wash every single day. A long stay would need rocket after rocket full of fresh air and water.

That is why the astronauts hold on to every bit they have. They run machines that take the stale part out of the air they breathe out. Then the machines make new oxygen out of water and add it back in, so the same air is good to breathe again.

The astronauts do the same with water. Their machines clean used wash water and even sweat until it is clear and safe to drink. The same water goes round and round, so a small load of cargo lasts a very long time.

Oxygen and cargo. A Moon home reuses its oxygen and water because the Moon has no air or rivers to give, and rockets from Earth can carry only a little cargo.

Next time you sip a cool glass of water, you can think of the cosy Moon home where every drop goes round and round, and drift off to sleep.