Respuesta :

Keeps oxygen intact within a circuit for the body
Provides protection from the effects of space's atmosphere pressure 
Weighs down the body to keep one on the floor of the planet/area they're on
Provides oxygen for them to breathe.
Protects the from the extreme cold.
They protect them from any small rocks that could harm them.
Also they provide a little drinking water for them when they are walking around. 

There are four. Hope that helps.