Biosphere

From Confederation Handwiki

Biosphere is the name given to the habitable area of an asteroid settlement. It consists of a cylindrical space hollowed out of the rock, which is then sealed and has a breathable atmosphere introduced. Usually the biosphere is planted, either as a park or as arable land, but occassionally, as in the case of the asteroid Sonora, the biosphere is flodded and turned into a giant freshwater lake.