Earth's biosphere is the sphere of life around the planet. Its organisms interact with their environment and each other, maintaining conditions on the planet conducive to life. Light from the Sun causes plants and algae to photosynthesize and thereby produce the oxygen that animals and microbes need. As a by-product of their respiration, animals and microbes in turn provide carbon dioxide, which plants require to grow. The oxygen atoms are used over and over again within the biosphere's oxygen cycle. There are many such cycles in a biosphere, with many creatures depending on other creatures for their survival.

Why Build a Biosphere for People?

At current estimates, it would cost around $22,000 to launch a medium pepperoni pizza to the International Space Station. For short space missions of less than two years it is cost effective to take along everything that is needed, as if one were embarking on...